Colleen T. Downs
Other affiliations: University of Natal
Bio: Colleen T. Downs is an academic researcher from University of KwaZulu-Natal. The author has contributed to research in topics: Population & Habitat. The author has an hindex of 31, co-authored 383 publications receiving 4967 citations. Previous affiliations of Colleen T. Downs include University of Natal.
Papers published on a yearly basis
TL;DR: The results corroborate those for the Neotropics and suggest that conservation of parrots globally would benefit from similar legislation introduced in other regions, such as the EU, which is responsible for more than 60% of global imports of wild parrots.
Abstract: Wild parrots represent one of the greatest commercial interests in the legal trade in wild birds. Although it is difficult to quantify, there is a considerable illegal trade in wild parrots. Thirty-six per cent of the world's parrot species are listed by the International Union for the Conservation of Nature as threatened or near threatened, and 55% of these are threatened to some degree by trade. In this paper, we investigate the impact of protection on the number of nests that failed because of nestlings being taken by humans (hereafter nest take) and on nesting success in parrots. We collate data on parrot nest take from published and unpublished studies from Africa, Asia and Australasia, including countries and sites with and without national and local parrot protection measures in place. Nest take was insignificant in Australia, where all studies were from areas with both local and national protection. For less developed countries, levels of nest take were variable between studies, spanning the whole range from 0 to 100%. Protection significantly reduced nest take and correspondingly increased nesting success. Our results corroborate those for the Neotropics; thus, the advantages of protection appear to be independent of geographical location or political and economic conditions. We analysed data on legal trade in wild-caught parrots before and after implementation of the 1992 Wild Bird Conservation Act (which practically eliminated import of parrots to the USA) and found that there was no apparent shift in parrot imports to other global regions from the Neotropics. We suggest that conservation of parrots globally would benefit from similar legislation introduced in other regions, such as the EU (15), which is responsible for more than 60% of global imports of wild parrots.
TL;DR: The Science Foundation Programme (SFP) at the University of KwaZulu Natal, Pietermaritzburg attempts to address past educational inequalities by providing disadvantaged matriculants with the skills, resources and self-confidence needed to embark on their tertiary studies as discussed by the authors.
Abstract: The Science Foundation Programme (SFP) at the University of KwaZulu Natal, Pietermaritzburg attempts to address past educational inequalities by providing disadvantaged matriculants with the skills, resources and self‐confidence needed to embark on their tertiary studies. Students entering the Programme typically adopt a surface approach to learning with emphasis being placed on high score achievement which results in a mark‐driven attitude towards assessment. Students also lack the metacognitive skills associated with a deep approach to learning. Within this mark‐driven culture, it is important to attempt to move students away from such a superficial approach to learning and assessment. Worldwide, self‐assessment practice has been gaining recognition, and it has been linked to the adoption of a deep approach to learning; self‐regulated learning and the development of metacognitive skills. In the biology module of the Programme, students are given two essay assignments, tasks that are routinely performed ...
TL;DR: In the authors' opinion, centralisation of wildlife rehabilitation to national or provincial government is a necessity, and it is suggested that guidelines of minimum standards should be developed in consultation with experienced rehabilitators, veterinarians and conservation scientists to be enforced by trained and dedicated conservation officials.
Abstract: The focus of wildlife rehabilitation is the survival of the individual animal, often leading to rehabilitators being in conflict with government wildlife officials, who regulate the industry and whose focus is on the security of entire wildlife communities. In South Africa, wildlife rehabilitation has been the focus of recent attention from the general public, government and academics, due mostly to the development and adoption of norms and standards for the management of primates. Our study was initiated to provide the first survey of rehabilitation centres in South Africa. Questionnaires were returned by 65% known rehabilitation centres in South Africa, including all nine Provinces, through which several thousand injured, diseased and orphaned animals pass each year. It is clear there is a need for rehabilitation centres in South Africa. However, due to a lack of scientific research on the efficacy of rehabilitation methods for care and release, and minimal post-release monitoring, wildlife rehabilitation techniques and protocols have been based on work experience and subjective intuition. In conjunction with a lack of funds, there may be negative impacts on individual animal welfare and survival, as well as on conservation efforts for wildlife communities. Similar issues have been documented in other regions of the world. In the authors' opinion, centralisation of wildlife rehabilitation to national or provincial government is a necessity. Furthermore, it is suggested that guidelines of minimum standards should be developed in consultation with experienced rehabilitators, veterinarians and conservation scientists; to be enforced by trained and dedicated conservation officials.
TL;DR: Frugivores not only accelerate dispersal, but also greatly enhance seed germination of all fleshy-fruited invasive alien species in this study.
Abstract: Many highly invasive plant species have fleshy fruits which are eaten by native frugivorous animals. These frugivores play an important role in long-distance seed dispersal, and may also affect germination success. The aim of this study was to determine whether generalist frugivores enhance or decrease seed germination of invasive alien species through pulp removal or seed coat abrasion, besides serving as dispersal agents. Fruits of four fleshy-fruited invasive alien plant species, namely Solanum mauritianum, Cinnamomum camphora, Lantana camara and Psidium guajava, were fed to three generalist avian frugivorous species, which have been observed feeding on these fruits in the wild. Seed retention time was recorded as this affects dispersal distance and the duration that seeds are exposed to the effects of the gut. Seeds removed from excreta, seeds from manually de-pulped fruit, and whole fruit were planted in soil trays housed in a greenhouse. Daily germination counts were done. Seed retention times differed significantly between bird species for all fruits, except those of C. camphora. However, all frugivores had a similar effect on the germination success of seeds of S. mauritianum, L. camara and P. guajava, showing that gut retention time was not important. Germination of seeds from manually de-pulped fruits did not differ from that of ingested seeds of all plant species, suggesting that seed coat abrasion was also not important. Pulp removal resulted in significantly higher germination rates, both in the two species with larger, multi-seeded fruit (S. mauritianum and P. guajava), and in the two species having single-seeded fruit with waxy exocarps (C. camphora and L. camara). Pulp removal also resulted in significantly earlier germination of L. camara and P. guajava seeds. Therefore, frugivores not only accelerate dispersal, but also greatly enhance seed germination of all fleshy-fruited invasive alien species in this study.
TL;DR: In this paper, the authors used camera traps at three sites differing in intensity of farmland use with capture-recapture models to assess the serval abundance and found that servals were mainly crepuscular and nocturnal.
Abstract: The Drakensberg Midlands, South Africa are experiencing unprecedented levels of habitat change. Despite the serval (Leptailurus serval) being a near-threatened wetland specialist, no studies have investigated their response to land use. To assess their abundance, we used camera trapping at 3 sites differing in intensity of farmland use with capture–recapture models. A total of 1,320 camera trap nights across the 3 sites yielded 26 and 28 servals. We detected no major difference in servals/100 km 2 among the 3 sites using spatially explicit maximumlikelihood (7.6 6 2.3; 6.5 6 2.7; 6.5 6 2.6) and Bayesian (7.7 6 1.6; 6.2 6 1.9; 6.9 6 2.1) methods in sites A, B, and C, respectively. Servals were mainly crepuscular and nocturnal. The Mardia–Watson–Wheeler test showed significant difference in activity in A and C compared with B, whereas it showed no difference between A and C. Servals avoided activity during the day in the intensively farmed B. Abundance analysis at the broader habitat scale may not have detected variation among sites. Differences need to be tested at smaller spatial scales. The statistical approaches in this study provide the 1st robust estimation of serval population size. This estimation of a medium-sized felid with changing land use can assist their management and conservation.
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201
01 Jan 2016
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30 Apr 1984
TL;DR: A review of the literature on optimal foraging can be found in this article, with a focus on the theoretical developments and the data that permit tests of the predictions, and the authors conclude that the simple models so far formulated are supported by available data and that they are optimistic about the value both now and in the future.
Abstract: Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.
TL;DR: This review applies classical models of thermal adaptation to predict variation in body temperature within and among populations of mammals and birds and relates these predictions to observations generated by comparative and experimental studies.
Abstract: During the last quarter of a century, the evolution of the thermal sensitivity of performance in ectotherms has become a major focus of research programs in evolutionary physiology. Graphical and mathematical models describe how the relationship between body temperature and performance, termed the performance function, should evolve in response to the thermal environment. Interspecific comparisons of the thermal sensitivity of locomotor performance have revealed that the performance function is evolutionarily labile in some taxa but is more conservative in others. A lack of heritable variation or weak selection on performance may explain the conservation of thermal physiology in certain groups, but evolutionary trade-offs do not appear to have been important constraints. Other aspects of thermal physiology, such as the thermal sensitivity of growth rate, have evolved rapidly in ectotherms. Despite the apparent lability of thermal physiology in some taxa, there is limited evidence that thermoregulatory behavior and thermal physiology are coadapted. Future studies should broaden taxonomic and phenotypic foci, while paying close attention to the assumptions of current theories.
TL;DR: A global map of zoogeographic regions is generated by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals, and it is shown that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere.
Abstract: Modern attempts to produce biogeographic maps focus on the distribution of species, and the maps are typically drawn without phylogenetic considerations. Here, we generate a global map of zoogeographic regions by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals. We identify 20 distinct zoogeographic regions, which are grouped into 11 larger realms. We document the lack of support for several regions previously defined based on distributional data and show that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere. We further show that the integration of phylogenetic information provides valuable insight on historical relationships among regions, permitting the identification of evolutionarily unique regions of the world.