With the advent of new technologies, animal locations are being collected at ever finer spatio-temporal scales. We review analytical methods for dealing with correlated data in the context of resource selection, including post hoc variance inflation techniques, ‘two-stage’ approaches based on models fit to each individual, generalized estimating equations and hierarchical mixed-effects models. These methods are applicable to a wide range of correlated data problems, but can be difficult to apply and remain especially challenging for use–availability sampling designs because the correlation structure for combinations of used and available points are not likely to follow common parametric forms. We also review emerging approaches to studying habitat selection that use fine-scale temporal data to arrive at biologically based definitions of available habitat, while naturally accounting for autocorrelation by modelling animal movement between telemetry locations. Sophisticated analyses that explicitly model correlation rather than consider it a nuisance, like mixed effects and state-space models, offer potentially novel insights into the process of resource selection, but additional work is needed to make them more generally applicable to large datasets based on the use–availability designs. Until then, variance inflation techniques and two-stage approaches should offer pragmatic and flexible approaches to modelling correlated data.

/pdf/correlation-and-studies-of-habitat-selection-problem-red-1xbyadq9wx.pdf

Correlation and studies of habitat selection: problem, red herring or opportunity?

The evolution of alternative male phenotypes is probably driven by male–male competition for access to reproductive females, but few studies have examined whether whole–organism performance capacities differ between male morphs, and if so whether any such differences affect fighting ability. We show how ontogenetic changes in performance and morphology have given rise to two distinct life–stage male morphs exhibiting different fighting tactics within the green anole lizard ( Anolis carolinensis ). Field studies show a bimodal distribution of adult males within a single population: larger ‘heavyweight’ males have relatively large heads and high bite forces for their size, whereas smaller ‘lightweight’ males have smaller heads and lower bite forces. In staged fights between size–matched heavyweight males, males with greater biting ability won more frequently, whereas in lightweight fights, males with greater jumping velocity and acceleration won more often. Because growth in reptiles is indeterminate, and the anole males examined are sexually mature, we propose that the heavyweight morph arose through selection against males with small heads and poor bite forces at the lightweight–heavyweight size transition. Our findings imply that one may not be able to predict male fighting success (and hence potential mating success) by examining aspects of male ‘quality’ at only one life stage.

/pdf/performance-capacity-fighting-tactics-and-the-evolution-of-3k2273k6lh.pdf

Performance capacity, fighting tactics and the evolution of life–stage male morphs in the green anole lizard (Anolis carolinensis)

Summary 1. Morphological characteristics (snout‐vent length, badge area, mass, limb and head measures) and whole-animal performance capacities (sprint speed, acceleration capacity, stamina and bite force) were measured in male lizards, Gallotia galloti . These males were also tested in paired staged contests to assess relative fighting capacity and to link these results to morphology and performance. 2. A multivariate analysis of the four performance features revealed a clear difference between the physiological capacities of winners vs losers, with bite force being the most important predictor of the outcome of fights. 3. The finding that bite performance is linked to dominance fits in with the high sexual dimorphism in head size in this species, as head size is a predictor of bite force performance. 4. Winners of contests also tended to have larger total areas of blue patches on their sides, suggesting that these badges convey information on the social status of the males. However, since no correlation was found between bite force and badge size, the patches seem to contain information on a component of fighting capacity other than bite force.

Morphology, performance and fighting capacity in male lizards, Gallotia galloti

The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics

Measurements of whole-organism performance traits have been useful in studies of adaptation and phenotype– environment correlations. Bite force capacities may be tightly linked to both the type and magnitude of the ecological challenges of food acquisition, mate acquisition, and antipredation in vertebrates. In the present study, we present technical details on bite meters and on measuring bite forces. The ability to take reliable measurements depends on specific features of the measuring device and on where in the mouth the bite is applied. Using both previously available and original data, we demonstrate several ecologically and evolutionarily relevant features of bite force measurements. First, maximal bite forces are repeatable among individuals across all vertebrates studied to date. Second, in ectotherms such as lizards, maximal bite forces are affected by body temperature and motivational states. Third, bite forces are strongly correlated with head size and shape. Fourth, bite forces correlate with features of prey of vertebrates. Finally, bite forces are linked to male dominance and correlated with social-display structures. Thus, bite force performance measures can be used as ‘traits’, and thus be used in integrative studies at multiple levels of organismal biology. Accordingly, bite force data will help our understanding of the functions, capacities, and evolution of jaw–cranial musculoskeletal systems. Moreover, a plethora of opportunities exist for the use of bite force measurements, and if methods are carefully applied, several levels of organismal and ecological organization can be integrated to aid our understanding of the ecology and evolution of vertebrate taxa. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 709–720.

Bite force in vertebrates: opportunities and caveats for use of a nonpareil whole-animal performance measure

Summary 1. Relationships between morphology, bite force capacity, prey handling efficiency and trophic niche were explored in two sympatric species of lacertid lizards, Podarcis melisellensis (Braun 1877) and Lacerta oxycephala Dumeril & Bibron 1839. 2. Head shape showed little variation, but head size (absolute and relative to snout‐ vent length, SVL) differed between species and sexes. Males have larger heads than females, both absolute and relative to their SVL. In absolute terms, male P. melisellensis have larger heads than male L. oxycephala , but the reverse case was true for the females. Relative to SVL, L. oxycephala have larger heads than P. melisellensis . 3. Bite force capacity was estimated by having the lizards bite on two metal plates, connected to a piezoelectric force transducer. Differences in maximal bite force between species and sexes paralleled differences in absolute head size. Differences in body size and head size explain the higher bite force of males (compared with females), but not the higher bite force of P. melisellensis (compared with L. oxycephala ). Among individual lizards, bite force correlated with body size and head size. 4. Prey handling efficiency, estimated by the time and number of bites needed to subdue a cricket in experimental conditions, also showed intersexual and interspecific variation. This variation corresponded to the differences in maximal bite capacity, suggesting that bite force is a determining factor in prey handling. Among individual lizards, both estimates of handling efficiency correlated with maximal bite force capacity. 5. Faecal pellet analyses suggested that in field conditions, males of both sexes select larger and harder prey than females. There was no difference between the species. The proportion of hard-bodied and large-sized prey items found in a lizard’s faeces correlated positively with its bite force capacity. 6. It is concluded that differences in head and body size, through their effect on bite force capacity, may affect prey selection, either directly, or via handling efficiency.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.2002.00696.x

Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards

Wide home ranges for widely foraging lizards.

Apart from certain species of the African clade, the lizard family Lacertidae has generally been described as consisting of active foragers. We made quantitative field observations of 14 species of lacertid lizards, mainly belonging to the more basal Eurasian clade. Our data show that sit-and-wait foraging is much more widespread in Lacertidae than previously alleged. We also investigated the influence of weather and times of day on foraging activity levels and conclude that for comparative purposes observations should be restricted to circumstances that are optimal for activity. We did not find sex differences in foraging behavior.

https://bioone.org/journals/journal-of-herpetology/volume-42/issue-1/07-136R1.1/Foraging-Mode-and-Its-Flexibility-in-Lacertid-Lizards-From-Europe/10.1670/07-136R1.1.pdf

Foraging Mode and Its Flexibility in Lacertid Lizards From Europe

Evolutionary changes in foraging style are often believed to require concurrent changes in a complex suite of morphological, physiological, behavioural and life-history traits. In lizards, species from families with a predominantly sit-and-wait foraging style tend to be more stocky and robust, with larger heads and mouths than species belonging to actively foraging families. Here, we test whether morphology and foraging behaviour show similar patterns of association within the family Lacertidae. We also examine the association of bite force abilities with morphology and foraging behaviour. Lacertid lizards exhibit considerable interspecific variation in foraging indices, and we found some evidence for a covariation between foraging style and body shape. However, the observed relationships are not always in line with the predictions. Also, the significance of the relationships varies with the evolutionary model used. Our results challenge the idea that foraging style is evolutionarily conservative and invariably associated with particular morphologies. It appears that the flexibility of foraging mode and its morphological correlates varies among lizard taxa.

D. Verwaijen

Papers

Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards

Wide home ranges for widely foraging lizards.

Foraging Mode and Its Flexibility in Lacertid Lizards From Europe

Does foraging mode mould morphology in lacertid lizards

Correlated evolution of thermal characteristics and foraging strategy in lacertid lizards