Showing papers in "Journal of Zoology in 1999"
TL;DR: The use of a compliant walking gait appears to be extremely rare among mammals and is most likely related to an initial primate adaptation to quadrupedal locomotion on terminal branches, which represents a previously unrecognized dynamic postural mechanism for maintenance of similar bone stresses and safety factors in both arboreal and terrestrial environments.
Abstract: It is now well recognized that terrestrial mammals can maintain equivalent bone stresses despite dramatic differences in body size through the adoption of extended limb positions during locomotion. However, this dynamic solution is not available to all mammals. Medium- and large-bodied arboreal mammals, such as anthropoid primates, must maintain relatively gracile and mobile limbs in order to manoeuvre in a discontinuous arboreal environment. But they must also use flexed (i.e. crouched) limb positions in order to maintain balance on arboreal substrates, thus subjecting their gracile limbs to relatively high loads. To determine how primates resolve this conflict between their kinematics and their morphology, five species of Old World monkeys were videotaped with lateral, frontal, and overhead cameras while they walked at a range of natural speeds along a runway and raised horizontal poles instrumented with a force platform. Kinematic and kinetic data on the forelimb show that during arboreal quadrupedalism, Old World monkeys do crouch when travelling on arboreal supports compared to the ground. Simultaneously, they lower vertical peak reaction forces and thereby reduce and reorient the peak resultant substrate reaction force, so that moment arms and moments are roughly equivalent on poles and the ground. This is accomplished through the adoption of a compliant walking gait characterized by high degrees of forelimb protraction, substantial elbow yield, low vertical oscillations of the body, and long contact times. The use of a compliant walking gait appears to be extremely rare among mammals and is most likely related to an initial primate adaptation to quadrupedal locomotion on terminal branches. This gait represents a previously unrecognized dynamic postural mechanism for maintenance of similar bone stresses and safety factors in both arboreal and terrestrial environments.
264 citations
TL;DR: Life-history traits of Rana temporaria were studied in an alpine French population and in the literature, and mean adult body length was greater in females than in males.
Abstract: Life-history traits of Rana temporaria were studied in an alpine French population and in the literature. In the living frogs, mean adult body length was greater in females than in males. Sexual dimorphism in body length was 0.109 using Lovich & Gibbon's (1992) formula, but tended to decrease with age. Age of adult frogs was assessed by skeletochronology, and age distribution was not significantly different between the sexes (range 4–15 years in males, 5–12 in females). Adult survival rate was about 0.80 in both sexes. Once maturity was reached, the total expected longevity was 6.1 years in males and 5.5 years in females. Age and body length were positively correlated in both sexes. The growth coefficient (K) was 0.47 in males, and 0.55 in females, mainly reflected as faster female growth between metamorphosis and maturation. Growth rate generally decreased before sexual maturity was reached. On average, females matured 1 year later than males. Newly metamorphosed froglets averaged 16.1 mm. When combined with published data from 12 European populations of R. temporaria, the following general patterns emerge. Mean adult body length is significantly greater in females than in males, and mean body length at maturity shows the same trend. Variation in mean age at maturity and in longevity are considerable among populations, but there is no consistent trend of difference between the sexes. Body length and age are correlated between males and females, i.e. populations with long and old males also have long and old females. Mean adult body length, mean body length at maturity, age at maturity, and longevity all increase with decreasing activity period. Adults exposed to a short activity period grow slower but attain a greater final length. Sexual dimorphism in body length generally increases as activity period gets shorter. Polygons describing norms of reaction for maturation in an age–body length space are similarly oriented in both sexes, but with a wider range in age for females. This is due to an older age at maturity for females in populations with a short activity season. Mean age and length at maturity are significantly correlated in females, but not in males, partly supporting the hypothesis that this species has a flexible pattern of development. Observed patterns are compared with predictions from life-history theory, paying attention to all life stages and environmental variation.
250 citations
TL;DR: Seasonal migration pattern and home range of radio-collared roe deer were studied in Lier, Norway, an area with a steep altitudinal gradient and a low population density of deer and it was concluded that these high elevation areas were probably of low quality.
Abstract: Seasonal migration pattern and home range of radio-collared roe deer (Capreolus capreolus) were studied in Lier, Norway, an area with a steep altitudinal gradient and a low population density of deer. Roe deer conformed to the usual pattern of temperate cervids with migration to low elevations during winter. Summer home-range size increased with increasing altitude, and only a small proportion of individuals had home ranges at high altitudes. It is concluded that these high elevation areas were probably of low quality. Time of spring migration was later in deer with a high elevation summer range. A lower frequency of females (30.0%) than males (61.5%) was stationary, and more females (30.0%) than males (0%) were long distance migrators (> 10 km). This supports an earlier hypothesis that migration patterns of roe deer are also influenced by social factors.
219 citations
TL;DR: The findings provisionally support the natal homing hypothesis for leatherback turtles, although several proximal nesting populations were indistinguishable, suggesting recent colonization or less precise natalHoming behaviour than documented for other marine turtle species.
Abstract: Analyses of mitochondrial (mt) DNA control region sequences from 175 leatherback turtles Dermochelys coriacea from 10 nesting colonies revealed shallow phylogenetic structuring of maternal lineages on a global scale. Eleven haplotypes were observed, and mean estimated sequence divergence, p = 0.00581, is much lower than the deepest nodes reported in global mtDNA surveys of the green turtle Chelonia mydas, loggerhead Caretta caretta, and ridley turtles Lepidochelys spp. The leatherback turtle is the product of an evolutionary trajectory originating at least 100 million years ago, yet the intraspecific phylogeny recorded in mitochondrial lineages may trace back less than 900 000 years. The gene genealogy and global distribution of mtDNA haplotypes indicate that leatherbacks may have radiated from a narrow refugium, possibly in the Indian‐Pacific during the early Pleistocene glaciation. Analysis of haplotype frequencies revealed that nesting populations are strongly subdivided globally (FST = 0.415), and within ocean basins (FST = 0.203‐0.253), despite the leatherback’s highly migratory nature. Within the Atlantic significant differences in haplotype frequency distributions and Nm values < 2 are observed in pairwise comparisons between St. Croix (U.S. Virgin Islands) and mainland Caribbean populations, and between Trinidad and the same mainland populations. These findings provisionally support the natal homing hypothesis for leatherback turtles, although several proximal nesting populations were indistinguishable, suggesting recent colonization or less precise natal homing behaviour than documented for other marine turtle species. The evidence of natal homing, manifested on ecological time scales, may be erased in some populations by rapid rookery turnover resulting from climatic fluctuation and the ephemeral nature of nesting habitat on a geological time scale. The evolutionary effective population size (Ne) is estimated from mtDNA data to be between 45 000 and 60 000, a value that exceeds current global census estimates of 26 000 to 43 000 adult females.
187 citations
TL;DR: Comparisons of hand and foot proportions demonstrate that Marmosa and Caluromys, didelphids that rely on vines or terminal branches, possess more prehensile extremities than Monodelphis, Didelphis, and Philander, which travel and feed mainly on the ground.
Abstract: The ability of some mammals to forage on vines or terminal branches depends upon their grasping extremities. This study tests the functional link between use of small-diameter supports and grasping abilities by comparing hand and foot proportions in didelphid marsupials. Metapodials and phalanges were measured for the hands and feet of six didelphid taxa characterized by different patterns of substrate use. Comparisons of hand and foot proportions demonstrate that Marmosa and Caluromys, didelphids that rely on vines or terminal branches, possess more prehensile extremities than Monodelphis, Didelphis, and Philander, which travel and feed mainly on the ground. Moreover, the proportions of the hand and foot of Marmosa and Caluromys are more similar to those of cheirogaleid primates than those of other didelphids. These morphological data corroborate the suggestion that the use of branches of small diameter was an important factor in the development of prehensile hands and feet in early primates.
177 citations
TL;DR: Multiple regression with phylogenetically independent contrasts indicates that interspecific variation in maximal speed is positively correlated with hindlimb span, but not significantly related to either body mass or body temperature.
Abstract: We measured sprint performance of phrynosomatid lizards and selected outgroups (n = 27 species). Maximal sprint running speeds were obtained with a new measurement technique, a high-speed treadmill (H.S.T.). Animals were measured at their approximate field-active body temperatures once on both of 2 consecutive days. Within species, individual variation in speed measurements was consistent between trial days and repeatabilities were similar to values reported previously for photocell-timed racetrack measurements. Multiple regression with phylogenetically independent contrasts indicates that interspecific variation in maximal speed is positively correlated with hindlimb span, but not significantly related to either body mass or body temperature. Among the three phrynosomatid subclades, sand lizards (Uma, Callisaurus, Cophosaurus, Holbrookia) have the highest sprint speeds and longest hindlimbs, horned lizards (Phrynosoma) exhibit the lowest speeds and shortest limbs, and the Sceloporus group (including Uta and Urosaurus) is intermediate in both speed and hindlimb span.
174 citations
TL;DR: Traditional categories of locomotor habit in mammals are rejected here in favour of a multivariate continuum based on morphological variables that fulfil predictions of limb design under biomechanical theory, which can be tied to limb mechanics and applied to both extant and extinct animals alike.
Abstract: Traditional categories of locomotor habit in mammals are largely based on variables that are continuous in nature, making intermediate forms difficult to evaluate quantitatively. Interpretations of these categories have varied greatly among authors, mainly owing to the inconsistent meanings ascribed to these essentially morphological variables. As a result, it is not clear whether these categories reflect any true locomotor influence, or if they can be applied in any form to non-mammalian taxa. In order to rectify these two difficulties, locomotor categories are rejected here in favour of a multivariate continuum. By basing this continuum on morphological variables that fulfil predictions of limb design under biomechanical theory, it can be tied to limb mechanics and applied to both extant and extinct animals alike. A series of such measurements were taken from a large sample of mammal and dinosaur hindlimb bones, and subjected to statistical testing. Patterns of variation in dinosaurs are similar to those seen in mammals, ranging between extremes traditionally designated as ‘cursorial’ and ‘graviportal’. An evaluation of dinosaur locomotor evolution in light of this continuum suggests that dinosaurs originated as small cursors, but that most lineages acquired a more mid-grade locomotor habit. Large taxa (sauropods, armoured ornithischians) were essentially graviportal, while smaller forms tended towards cursoriality; only coelurosaur theropods developed cursoriality at large body sizes. The discrepancy between large, graviportal herbivores and large, mid-grade to cursorial carnivores in Mesozoic communities argues against pursuit predation as a major influence in dinosaur locomotor evolution.
169 citations
TL;DR: In both high duty and low duty cycle echolocating bats the relationship between body size and dominant call frequency was best described by a linear model, and it is proposed that perch hunting was central in the development of the high duty cycle approach to eCholocation.
Abstract: In this study we explored quantitatively the relationships between the size of bats, the frequencies in their echolocation calls, and the incidence of moths and beetles in their diets. We focused on the predictions of the allotonic frequency hypothesis which states that some insectivorous bats increase their access to moths that can hear echolocation calls by shifting to frequencies to which the ears of these insects are less sensitive. The hypothesis predicts that the frequencies dominating the echolocation calls of bats may be correlated with the incidence of moths in their diets. We collected data for 62 species of bats that take airborne prey, usually flying insects, 25 species of high duty cycle echolocating bats (Rhinolophidae and Hipposideridae) and 37 species that are low duty cycle echolocators (Vespertilionidae and Molossidae). For bats whose echolocation calls are dominated by frequencies 100 kHz, the relationship was not statistically significant, suggesting that morphological characteristics rather than echolocation call frequency may limit the range of potential prey items. Our analyses also demonstrate the importance of jaw morphology as a predictor of the incidence of beetles or moths in the diets of bats, and reveal that generally bigger species (as defined by forearm length) use echolocation calls dominated by lower frequencies than smaller species. In both high duty and low duty cycle echolocating bats the relationship between body size and dominant call frequency was best described by a linear model. We also propose that perch hunting was central in the development of the high duty cycle approach to echolocation.
162 citations
TL;DR: In this article, the calls of five odontocete cetaceans, the false killer whale P. crassidens, short-finned pilot whale G. macrorhynchus, G. melas, white-beaked dolphin L. albirostris and Risso's dolphin G. griseus, were analyzed and summarized quantitatively.
Abstract: Whistle vocalizations of five odontocete cetaceans, the false killer whale P. crassidens, short-finned pilot whale G. macrorhynchus, long-finned pilot whale G. melas, white-beaked dolphin L. albirostris and Risso's dolphin G. griseus, were analysed and summarized quantitatively. Recordings were acquired from a number of locations and encounters. Significant differences were found between species and, to a lesser extent, between locations. The calls of the two pilot whale species are distinct despite their close relatedness, and similar size and morphology. This may be due to selection pressures to maintain distinctiveness. The variance was partitioned into between-species, between-location (within species) and within-location factors. For the frequency variables, variation between-species is high relative to variation between locations. Thus geographic variation is a relatively minor effect, compared to the many processes which cause interspecific differences. The within-location component includes such factors as social context, behaviour and group composition. This component is of a similar magnitude to the between-species component, indicating that whistles vary considerably with these factors. Significant between-location differences may be attributable to these confounding factors. For whistle duration, most of the variation occurred within location. There is less significant variation in duration across species compared with the frequency measures. This study highlights the need to collect samples across all potential strata whenever possible, and provides a framework for future, more comprehensive work.
147 citations
TL;DR: It is proposed that tracheal elongation serves to exaggerate the apparent size of a vocalizing bird, and this ‘size exaggeration’ hypothesis is found to be consistent with current theories of avian vocal production and a wide range of comparative ecological and behavioural data.
Abstract: At least 60 bird species possess an elongated trachea that typically forms loops or coils within the sternum or thorax. This peculiar trait has been known for centuries, and a wide variety of hypotheses have been proposed for its function. However, none of these hypotheses adequately accounts for its existence in all of the diverse bird species and habitats in which it is found. In this paper it is proposed that tracheal elongation serves to exaggerate the apparent size of a vocalizing bird. In normal birds, trachea length is correlated with body size, and thus the acoustic correlates of trachea length in bird calls could convey information about size. By manipulating such an acoustic cue (formant frequency dispersion), tracheal elongation allows a caller to duplicate sounds produced by a larger bird. Unlike previously-proposed hypotheses, this ‘size exaggeration’ hypothesis is found to be consistent with current theories of avian vocal production and a wide range of comparative ecological and behavioural data. A number of new predictions of the hypothesis are found to be upheld. Finally, tracheal elongation is considered as a possible example of ‘sensory exploitation’, and its ultimate functional significance in mate choice and/or territoriality is discussed.
139 citations
TL;DR: Results of chi-square, log-linear, R×C, and Kruskal–Wallis tests demonstrate that feeding behaviours vary significantly with fruit hardness both within and between species.
Abstract: Most New World leaf-nosed bats (Phyllostomidae) are frugivores. Many of these species are sympatric and mechanisms of resource partitioning including vertical stratification and divergent foraging strategies have been described. This study investigates a previously unexplored but potentially significant factor in resource partitioning: the relationship between feeding behaviour and fruit hardness. Data summarizing ingestive and fruit processing behaviours were collected during feeding experiments from five sympatric frugivorous phyllostomid species: Artibeus jamaicensis , Dermanura phaeotis , Sturnira lilium , Carollia perspicillata , and Glossophaga soricina . Individuals were the subjects of feeding experiments that consisted of eating hard and soft fruits of similar size, shape, and mass. Variables analysed from videotapes of the experiments describe how fruits are placed in the mouth during ingestion, the frequency of head movements during biting, the number of bites used to remove a piece of fruit, and the number of chews used to process each mouthful of fruit. Results of chi-square, log-linear, R×C, and Kruskal–Wallis tests demonstrate that feeding behaviours vary significantly with fruit hardness both within and between species. Artibeus , Dermanura , and Sturnira are behaviourally specialized for feeding on relatively hard fruits. However, Carollia , and probably Glossophaga , lack these behavioural specializations. Both mechanical and ecological implications of intra- and interspecific behavioural variation are discussed. Differences in fruit handling behaviour are also used to make explicit predictions regarding interspecific variation in masticatory morphology. This study demonstrates that the relationship between fruit hardness and feeding behaviour may be an integral part of frugivore ecology. Overall, resource partitioning among phyllostomid frugivores is a result of complex interactions among and between bats and their food plants. Controlled experimental studies such as this one provide a crucial means of dissecting these complex interactions and gaining insight into the basis of frugivore diversity.
TL;DR: Examination of demographics, dispersal, sex-related behaviour, group structure, and genetic similarities of female feral pigs Sus scrofa on the Chaparral Wildlife Management Area in southern Texas indicated that genetic relationships of feral pigs played a role in observed population structure.
Abstract: We examined demographics, dispersal, sex-related behaviour, group structure, and genetic similarities of female feral pigs Sus scrofa on the Chaparral Wildlife Management Area in southern Texas from June 1993 to December 1995. Cumulative and seasonal ranges and core areas were calculated for 18 female pigs representing three distinct sounders. Simultaneous pairs of radio locations were used to assess behavioural associations among pigs, and DNA fingerprinting was used to determine genetic similarity. Behavioural and spatial associations largely corresponded to genetic relationships. Similarity of behavioural dendrograms to genetic dendrograms indicated that genetic relationships of feral pigs played a role in observed population structure. A single discrepancy between genetic and behavioural dendrograms suggested two animals dispersed to an adjacent sounder. Also, one sounder appeared to have been created by fission from a larger, adjacent sounder. Factors that are important keys in understanding the association between genetics and behaviour of feral pigs include dispersal, climate, habitat quality, population densities, and sex-related behaviour.
TL;DR: By supplying abundant food in the laboratory, the hypothesis that gravid females are anorexic is tested and the interactions among feeding, thermoregulation and reproductive condition are examined; the evidence slightly favours physiological suppression of appetite.
Abstract: Constraints on time and energy suggest that animals often will have to forgo one activity in favour of another. In the field, gravid garter snakes, Thamnophis elegans, eat little or nothing, especially late in pregnancy. In addition, they spend considerable time basking, presumably to aid development of their progeny. Apparently, therefore, a conflict exists between feeding and behaviours related to gestation. Alternatively, low feeding levels in the field might reflect reduced ability to catch food while gravid, or anorexia, attributable either to reduced space in the gut or to physiological suppression of appetite. In this study, by supplying abundant food in the laboratory, we test the hypothesis that gravid females are anorexic; we also examine the interactions among feeding, thermoregulation and reproductive condition. Typically, gravid females, whether fed or not, spent most of their time at the warm end of a gradient, as did fed non-gravid snakes; unfed non-gravid females spent significantly less time at the warm end. However, gravid snakes, even when presented with food ad libitum, ate less than non-gravid snakes, suggesting that they are anorexic while pregnant. Feeding and thermoregulatory behaviours of gravid females changed around the time of parturition (increased feeding, reduced warming rate). Comparable changes are seen in animals in the field, and are correlated with changes in movement pattern. Evidently, the tendency to eat little food is carried over into the laboratory, even when apparent proximate causes of the behaviour are removed. Although we cannot distinguish clearly between the two potential causes of anorexia, the evidence slightly favours physiological suppression of appetite. Physiological suppression of appetite while gravid would ensure that the urge to forage rather than thermoregulate does not diminish the chances of present reproductive success. By contrast, non-gravid snakes, faced with a shortage of food, lower their body temperature and reduce their metabolic costs.
TL;DR: Group dynamics of humpback dolphins Sousa chinensis inhabiting the Algoa Bay region on the south Eastern Cape coast of South Africa, were investigated by means of boat-based photo-identification surveys undertaken between May 1991 and May 1994 to suggest a minimum of a 3-year calving interval.
Abstract: Group dynamics of humpback dolphins Sousa chinensis inhabiting the Algoa Bay region on the south Eastern Cape coast of South Africa, were investigated by means of boat-based photo-identification surveys undertaken between May 1991 and May 1994 Groups of humpback dolphins varied in size from three to 24 animals (x = seven), with adults representing almost two-thirds of the group members Births occurred predominantly in summer Some females, however, may also cycle outside of the apparent summer breeding season, perhaps indicating a secondary winter season Circumstantial evidence suggests a minimum of a 3-year calving interval Maternal care lasts at least 3–4 years, but female–calf separation is seemingly not related to the female's next pregnancy Humpback dolphins displayed varying degrees of residence/fidelity to Algoa Bay Although a few individuals may possibly be classified as ‘resident’, most dolphins were infrequent visitors in the Bay and seem to be transient The social system of humpback dolphins appears to be fluid with only casual and short-lasting affiliations Strong bonds between individuals other than mothers and calves are uncommon Lack of consistency in the group membership appears to be the general pattern The weak site fidelity and possibly extensive long-range movement of the majority of dolphins may contribute to the dynamic nature of humpback dolphin groups There is probably some form of segregation between sex and/or age classes among humpback dolphins in Eastern Cape waters The nature and extent of this segregation, however, is not yet sufficiently understood It is likely that the degree of site fidelity displayed by female humpback dolphins is related to their reproductive stage and increases during the nursing period Mate-searching behaviour of male humpback dolphins is the most likely reproductive strategy of the species
TL;DR: The effects of roost temperature and colony size on reproductive success of colonies of M. myotis located in buildings and high average roost temperatures favoured development of juveniles but did not influence mortality.
Abstract: Some cave-dwelling bat species such as Myotis myotis now also roost in buildings in parts of their range. I studied the effects of roost temperature and colony size on reproductive success of colonies of M. myotis located in buildings. Temperatures in attics fluctuated considerably and altered the thermal conditions at the roost during the breeding season. Inter-colony variation was recorded with respect to factors indicating reproductive success (number, growth, and mortality of juveniles until fledging). However, over-winter survival varied more between years than between colonies. Colony size did not influence development or mortality of juveniles. High average roost temperatures favoured development of juveniles but did not influence mortality. Unlike the situation in caves, large colony sizes are not advantageous in buildings
TL;DR: Body sizes were studied over a 10-year period in an area of north-eastern Belarus, before and after the invasion by American mink, and data are presented on interspecific interactions to provide direct evidence for the aggressive nature of inter-specific relations.
Abstract: Body sizes of European mink (Mustela lutreola L.), polecat (M. putorius L.) and American mink (M. vison Schreber) were studied over a 10-year period in an area of north-eastern Belarus, before and after the invasion by American mink, and data are presented on interspecific interactions. On arrival in the study area American mink males were larger than males of European mink and polecat, and American mink females were larger than females of the other species. After arrival of the American mink its mean body size decreased, whilst the resident male and female European mink and female polecat increased as measured in absolute mass, length and relative mass. The observations suggest a strong character convergence most plausibly explained as a response to the invading exotic by the residents as well as in the invading species itself, whilst a divergence had been expected. There was no evidence to show whether these differences were genetically based. The body size data are consistent with the hypothesis that European mink, and to a lesser extent polecat, are responding to direct aggression from American mink (rather than merely competing for resources), with the smaller individual European mink being more likely to disappear first. We provide direct evidence for the aggressive nature of inter-specific relations from observations using radio-tracking: all observed inter-specific interactions were aggressive, significantly more so than intraspecific encounters, causing the European mink to flee, and several left the study area altogether. Implications for niche theory and for conservation management are discussed.
TL;DR: A method is described for assigning faeces to these three mustelid species, based on analysis of DNA extracted from their scats, and it is shown that the approach provided an efficient method of species identification.
Abstract: The abundance of mink, otter, and polecat may be inferred from records of their scats, and the feeding biology of the species is often studied by analysis of skeletal remains and other hard parts in faeces. However, in some situations it is difficult to distinguish between faeces from these three mustelid species. A method is described for assigning faeces to these three mustelid species, based on analysis of DNA extracted from their scats. Mustelid-specific primers were developed for PCR amplification of a part of the mitochondrial cytochrome b gene, and two restriction enzymes were found to detect species-specific sequence variation. Analysis of DNA from different faecal samples showed that the results were reproducible and that the approach provided an efficient method of species identification.
TL;DR: Variation in sett density, group size and territory size supported the hypothesis that badger group and territory sizes are influenced by habitat type, and was further supported by analyses of data from other studies in the British Isles.
Abstract: This study investigates how habitat variation affects sett density, the number of animals per social group and group territory size in the badger (Meles meles). Identical methods were applied in three habitat types: lowland parkland with mixed woodland, pastoral farmland and upland rough pasture with moorland, representing areas of presumed good, medium and poor badger habitat, respectively. Contiguous main setts were identified and bait-marking was used to estimate territory size. Group size was estimated by direct enumeration. Variation in sett density, group size and territory size supported the hypothesis that badger group and territory size are influenced by habitat type. This was further supported by analyses of data from other studies in the British Isles. The implications for badger spatial ecology, badger survey techniques and the badger's role in the epidemiology of TB are discussed.
TL;DR: Long bones from a taxonomically diverse assemblage of extant terrestrial mammals, spanning more than three orders of magnitude in body mass, have been measured in order to evaluate earlier models proposed for limb allometry as a means of physically coping with increased body size in large species.
Abstract: Long bones from a taxonomically diverse assemblage of extant terrestrial mammals, spanning more than three orders of magnitude in body mass, have been measured in order to evaluate earlier models proposed for limb allometry as a means of physically coping with increased body size in large species. Linear regression models are unable to explain long bone scaling across a large size range of mammals, as differential scaling is present in large and small species and smaller species tend to approach geometric similarity to a considerably greater extent than larger species. Attempting to explain the morphology of the appendicular skeleton across the large size range of terrestrial Mammalia by means of a standard power function will probably inevitably lead to oversimplification, concealing underlying adaptations for coping with increased size. These include differences in limb posture, decrease in locomotory potential and greater duty factors during fast locomotion in large animals compared to anatomically similar smaller forms, and differential scaling of the appendicular skeleton in small and large mammals.
TL;DR: The age at maturity increased with body size in the 17 populations of T. hermanni in Greece, while the Bertalanffy growth constant decreased with bodysize, suggesting that differences between populations were adaptive rather than the result of short-term disturbance.
Abstract: Seventeen populations of T. hermanni in Greece differed substantially in mean adult body size, over a range of about one and a half times in length and three times in mass. Females were the larger sex in all populations; the degree of sexual size dimorphism did not vary with mean body size. The proximate cause of the variation of body size among populations was differences in the duration of growth, rather than egg or hatchling size or the growth rates of juveniles. The age at maturity (α) increased with body size in the 17 populations, while the Bertalanffy growth constant (k) decreased with body size. The quantities αM and M/k (where M is the instantaneous mortality rate) were invariant with body size, suggesting that differences between populations were adaptive rather than the result of short-term disturbance. Body size was greater in cooler areas, and increased with both latitude and altitude. This pattern is opposite to that found in most ectotherms (the reverse Bergmann's rule), and to that which occurs between tortoise species. Several hypotheses about the possible ultimate causes of variation of body size were rejected, including adaptation to long-term habitat disturbance (land use), character displacement, social factors, energetics, thermoregulation, r-K selection, the length of the season available for incubation, or differences in juvenile mortality. The most likely ultimate cause of size variation between sites is differences in adult mortality, the correlation with environmental temperature being through the frequency of fires.
TL;DR: Mandibular rotation in lieu of depression and elevation simplifies jaw movements made by a smaller uniquely modified muscle mass over shorter distances, therefore increasing the speed with which anteaters can ingest food, and complements the extremely rapid tongue protrusion–retraction cycle.
Abstract: The edentulous giant anteater (Myrmecophaga tridactyla) ingests food using a slender, elongated sticky tongue which can project to a distance greater than the cranial length. A large and elongated hyoid apparatus, including a long stylohyal, epihyal, reduced ceratohyal and fused basihyal-thyrohyal fused to a partially ossified thyroid cartilage, supports the tongue. The fusion pattern and relative hyoid element sizes in adult Myrmecophaga differ from those in other xenarthran anteaters, tree and ground sloths, and armadillos. The hyoid bones have synovial joints with articular surfaces permitting great freedom of movement. A unique hyoid muscle arrangement enables Myrmecophaga to project the tongue with great speed and precise positional control. This muscle arrangement combined with an elongated secondary palate, accommodates the retracted tongue within the oropharynx without compromising the animal's ability to breathe. Maximum gape is reached at a few degrees of mandibular depression, but the oral opening is increased to 2 cm by the extreme length of the anterior facial region. Gape is further increased by medial rotation and depression of the unfused mandibular rami at the mental symphysis. This movement, even without mandibular depression, permits protraction and retraction of the elongated tongue. Mandibular rotation in lieu of depression and elevation simplifies jaw movements made by a smaller uniquely modified muscle mass over shorter distances, therefore increasing the speed with which anteaters can ingest food, and complements the extremely rapid tongue protrusion–retraction cycle.
TL;DR: The stomach contents of museum specimens and specific literature records are used to describe the food habits of a basal clade of macrostomatan snakes ‐ the erycine boas (Erycinae) with an emphasis on the North American Charina bottae.
Abstract: The Macrostomata accounts for more than 85% of extant snakes and is characterized by increased mobility of the jaws and increased gape size. We used stomach contents of museum specimens and specific literature records to describe the food habits of a basal clade of macrostomatan snakes – the erycine boas (Erycinae) – with an emphasis on the North American Charina bottae. Mammals, lizards, birds, and squamate eggs composed 66%, 17%, 7%, and 5%, respectively, of the prey of C. bottae. Smaller C. bottae fed on squamate eggs and lizards, whereas larger snakes added mammals and birds to their diet, and ceased to take squamate eggs. Ten of 12 snakes with multiple prey had eaten nestling birds or mammals, and snakes that ate multiple prey were not significantly larger than those that had single prey. Charina trivirgata and C. reinhardtii also prey on mammals, whereas species of Eryx feed mainly on mammalian prey, but also eat lizards and occasionally birds. Evolutionarily more basal groups of snakes primarily feed on elongate prey, which suggests that innovations of the feeding apparatus of macrostomatans allowed these snakes to eat heavier and bulkier prey, particularly mammals. Erycines appeared and diversified at approximately the same geological time as rodents, suggesting that rodents perhaps constituted an abundant prey resource that favoured the diversification of early macrostomatans.
TL;DR: It is suggested that more extensive introgression in the isolated island populations has resulted in an increase in hybrid fitness by an accumulation of fertile individuals of mixed ancestry acting as bridges for gene exchange.
Abstract: Breeding data for pied flycatchers Ficedula hypoleuca and collared flycatchers F. albicollis, from 47 localities in the Czech Republic and Slovakia, were analysed. We show that co-existence and hybridization were mainly restricted to a rather narrow, latitudinal cline. The distribution of the two flycatchers coincides with topography and habitat, collared flycatchers dominating in warmer habitats than pied flycatchers. Maintained co-existence within the same locality was the exception rather than the rule and most matings occurred in allopatry. In sympatry hybridization occurred at a frequency that was much lower than expected from random mating. Hybrids had low hatching success but some hybrids were apparently fertile. Shortage of conspecific mates may explain why individual birds engage in mixed species pairs. The proportion of pied flycatchers that was involved in mixed pairs was high and increased with decreasing relative frequencies of pied flycatchers in the population. The proportion of collared flycatchers involved in mixed pairs was low, reflecting the higher relative frequency of this species in most mixed populations. Comparisons suggest that fewer hybrids are breeding in the Central European, clinal hybrid zone than in the isolated hybrid zones of the Baltic Isles. Moreover, hybrid fertility was apparently higher in the island zones than in the clinal zone. We suggest that more extensive introgression in the isolated island populations has resulted in an increase in hybrid fitness by an accumulation of fertile individuals of mixed ancestry (i.e. F2, F3 ...F n-hybrids) acting as bridges for gene exchange. Differences in the dynamics of the two classes of hybrid zones, especially in pattern of gene flow, may explain these differences in frequency and fertility of hybrids.
TL;DR: The selection of roost cavities by the threatened New Zealand long-tailed bat Chalinolobus tuberculatus was examined in unmodified temperate southern beech Nothofagus rainforest in Fiordland, New Zealand as mentioned in this paper.
Abstract: The selection of roost cavities by the threatened New Zealand long-tailed bat Chalinolobus tuberculatus was examined in unmodified temperate southern beech Nothofagus rainforest in Fiordland, New Zealand. We radio-tracked 73 bats during spring–autumn of 1993–1997 to 155 day roosts, all of which were in trees. One hundred and forty-nine roosts were in cavities: 84 in live trunks, 33 in dead trunks, 32 in large branches (seven in dead branches, 25 in live); and the remaining six (occupied by solitary bats) were beneath loose bark. We compared characteristics of the 84 roost cavities in live trunks with 57 random available cavities also in live trunks. Cavities used by C. tuberculatus were not a random subset of available cavities. In comparison to available cavities, bat roosts were all located in knot hole cavities, were high from the ground, and had little surrounding vegetation. All roosts were dry inside. Bats used a higher proportion of cavities which had medium sized entrances and internal cavities, and thicker cavity walls. A logistic regression model incorporating nine cavity variables classified roost and available cavities correctly 97% and 91% of the time, respectively. Distance to the nearest vegetation, cavity condition (wet or dry inside), height from the ground, and to a lesser extent internal cavity height, explained significant proportions of the variation between roost and available cavities. Bats changed roost sites virtually every day and it appeared that suitable cavities were abundant in the unlogged forests of the study area. It is unlikely that modified forests and forests managed for timber production contain such a large pool of potential roosting cavities.
TL;DR: Large signal bandwidths facilitate highly accurate target localization in terms of both range and angle estimation and can thus be interpreted as an adaptation to foraging in the highly cluttered environment of the forest understorey.
Abstract: Echolocation signal design in nine syntopic vespertilionid bats from the Malaysian rain forest understorey was studied. Four species of Kerivoula, two species of Phoniscus (Kerivoulinae) and three species of Murina (Murininae) all emitted calls that are typical of species that glean insects from surfaces: broadband, frequency-modulated (FM) calls of low intensity and short duration. However, calls were highly distinctive in the use of very large bandwidths (range: 89–123 kHz) and extremely high frequencies (start frequency 152–180 kHz; end frequency 43–86 kHz). Furthermore, calls were produced in groups of 2–15 at very high pulse repetition rates (37–105 Hz). The functional significance of these characteristics with respect to foraging strategy is discussed. Large signal bandwidths facilitate highly accurate target localization in terms of both range and angle estimation and can thus be interpreted as an adaptation to foraging in the highly cluttered environment of the forest understorey. The use of high frequencies so far in excess of those seen in other FM gleaning bats of the same size is less easily explained, but may represent a mechanism by which these species distinguish prey items using echolocation alone, without recourse to visual or auditory cues. Species exhibited differences in echolocation parameters, particularly the end frequency and the number of calls per group of calls. The two subfamilies differed from each other in multivariate space derived from echolocation parameters; calls of the Murininae were of lower frequency than the Kerivoulinae and were typically produced in smaller groups or singly. Within the subfamilies there was considerable overlap between species of Murina, but the Kerivoula spp. were clearly distinct from one another but not from the two Phoniscus spp.
TL;DR: The abundance of the primates in the different forest types was shown to be a function of food availability, and the smaller-bodied species were more abundant in the forest that was richer in fruiting trees, while they were absent from a monodominant forest.
Abstract: A primate community was studied in a fluvial tropical rain forest island, in the northernmost part of Brazilian Amazonia, in the State of Roraima. Density and biomass were determined, and the differences between the forest types were assessed. The line-transect method was used from the east towards the centre of the island. No previous studies had been carried out in this remote undisturbed area. Density and biomass varied between the forest types, as well as between frugivorous primates; the smaller-bodied species were more abundant in the forest that was richer in fruiting trees, while they were absent from a monodominant forest. The folivorous, or partly folivorous, primates were abundant in those forests with less fruiting trees. The abundance of the primates in the different forest types was shown to be a function of food availability.
TL;DR: This is the first study of tawny owl diet in spruce forests in Britain and highlights the value of such large-scale dynamic habitats for rodent populations and their predators.
Abstract: The diet of tawny owls Strix aluco was determined from pellets and prey items in owl nests in Kielder Forest, a planted spruce forest in northern England. Field voles Microtus agrestis were their most important food, and formed the highest proportion of tawny owl diet in winter and early spring. Common shrews Sorex araneus, common frogs Rana temporaria and birds were taken more frequently in late spring and summer. Clear cuts, areas from which timber had been felled at the end of the rotation, provided the main field vole habitat in the forest and remained suitable for voles for 10–15 years after re-planting. Field vole abundance was measured three times a year on numerous clear cuts throughout the study area using a vole sign index based on fresh grass clippings in runways. Tawny owls responded functionally to the 3 to 4-year cycles of field vole abundance. In years when voles were scarce, adult owls took more common shrews and common frogs, as determined from pellet analysis. In contrast, more bird prey was fed to nestlings when field voles were scarce, as determined from prey items in nests. The proportions of the main prey in nests changed over a 19-year period. More bank voles Clethrionomys glareolus and wood mice Apodemus sylvaticus occurred in every year after 1992 than in any year before this. Numbers of wood mice in owl nests increased significantly throughout the study period, whereas bank vole numbers exhibited non-cyclic, multi-annual fluctuations that were unrelated to field vole cycles. It is argued that fluctuations in rodent prey reflected changes in rodent guilds in the study area; reasons for this are discussed. This is the first study of tawny owl diet in spruce forests in Britain and highlights the value of such large-scale dynamic habitats for rodent populations and their predators.
TL;DR: Comparisons showed roe deer to be highly selective, whilst red deer ate plants in proportions similar to their availability, whilst the use of some forb species by red deer in summer may limit their availability to roe Deer in winter.
Abstract: Diets of red Cervus elaphus and roe Capreolus capreolus deer in Scottish plantation forests were assessed by botanical and chemical analyses of 144 rumen samples. Samples were taken for summer and winter from four forests with a range of deer densities and ratios. Red deer ate mainly grasses in summer, and a mixture of sedges, rushes, grasses and heaths (ericoid plants) in winter. Roe deer ate predominantly forbs (herbaceous plants other than graminoids) in summer, and a mixture of forbs, heaths and tree and shrub browse in winter. The two species ate significantly different quantities of forbs and grasses (P < 0.001). Both species ate more grasses and forbs in summer, and more heaths in winter (P < 0.05). There were few differences between forests for either red or roe deer in diet composition or its seasonal variation. Washed rumen contents of roe deer contained more nitrogen than did those of red deer (P < 0.05) in both seasons, and both species contained more nitrogen in summer than in winter (P < 0.05). Proportions of the main plant categories within rumens were compared with their abundance recorded in the ground flora. These comparisons showed roe deer to be highly selective, whilst red deer ate plants in proportions similar to their availability. Niche overlap increased and dietary niche breadths widened during the winter. The main overlap was for heaths Calluna vulgaris and Vaccinium myrtillus in winter. However, C. vulgaris is widespread and common and competition was considered to be more likely for forbs and possibly V. myrtillus: the use of some forb species by red deer in summer may limit their availability to roe deer in winter, when they remain an important dietary item. Consideration of the different digestive specializations of the two species suggested that any dietary competition is likely to affect roe deer more than red deer.
TL;DR: The review shows that there is relatively little seasonal variation in the diet composition, which is more closely correlated to the habitat than to the season.
Abstract: We summarize the information on the diet of roe deer Capreolus capreolus found in 33 European studies. After giving a short overview of the differences between the existing studies, we compare the information for each season. We submit the information, summarized in a matrix of 83 cases on 10 food groups, to a detrended correspondence analysis (DCA) and a two-way indicator species analysis (TWINSPAN). We calculate weighted averages grouping the information by season, habitat, research method and their crossproducts. The weighted averages are also used as input for a multivariate ratio analysis. Since the available food items dictate the possible diet composition we further investigate the influence of the habitat on the reported food selection. The influence of season on the diet composition is compared with the effect of the habitat, and other factors such as research method and geographical location of the study site. The review shows that there is relatively little seasonal variation in the diet composition, which is more closely correlated to the habitat than to the season.
TL;DR: No evidence was found to suggest that male and female crested and smooth newts have adapted to different feeding strategies, and the results are interpreted as primarily concordant with theories on fecundity selection.
Abstract: Morphometric data from Fennoscandian populations of the crested newt Triturus cristatus and the smooth newt Triturus vulgaris were analysed for the presence of sexual size and shape dimorphism. The data sets included nine body-related and nine head-related measurements and were examined with univariate, bivariate and multivariate methods. Sexual dimorphism was demonstrated in both species. The separation of specimens was highly related to sex. Although the expression of sexual dimorphism differed between the two species, some patterns were shared. These are discussed in terms of evolution of intersexual dimorphism according to models of ecology, fecundity and sexual selection. In multivariate analyses, sexual dimorphism was restricted to body-related variables such as standard length and distance of extremities (with high values for females), contrasting against cloaca and limb-related characters (with high values for males). In both species, the ‘distance of extremities’ measure (i.e. trunk length) was one of the strongest sexually dimorphic traits. No evidence of sexual dimorphism in head morphology was found. The results are interpreted as primarily concordant with theories on fecundity selection. For example, it has been suggested that females with larger trunk volumes increase their reproductive capacity. The fact that males had longer extremities, in relation to other characters measured, could be attributed to sexual selection. Long limbs in male newts may be beneficial for courtship performance. Since head-related characters did not show any patterns of sexual dimorphism, no evidence was found to suggest that male and female crested and smooth newts have adapted to different feeding strategies.