Wild Mammal Populations Research Articles

Age-related reproductive variation in a wild marine mammal population

Life history theory predicts a change in reproduction success with age as energy resources are limited and must be allocated effectively to maximize reproduction and survival. In this study, we use three reproductive performance measures, maternal expenditure, offspring weaning mass, and first-year survival, to investigate the role that maternal age plays in successful reproduction. Long-term uninterrupted life history data available for Marion Island’s southern elephant seals and mass change estimates from photogrammetry data allow for assessment of age-related reproduction performance and trade-offs. Known-aged adult females were photographed for photogrammetric mass estimation (n = 29) and their pups weighed at weaning during the 2009 breeding season. Maternal age and proportional mass loss positively influenced pup weaning mass. In turn, first-year pup return rates (as a proxy for survival) were assessed through the intensive mark–recapture program. Pup survival increased with female age and weaning mass. Pups of young females aged 3–6 years have a lower first-year survival probability compared with pups of older and larger females.

PATHOLOGY OF SARCOPTIC MANGE IN RED FOXES (VULPES VULPES): MACROSCOPIC AND HISTOLOGIC CHARACTERIZATION OF THREE DISEASE STAGES

Sarcoptic mange is a highly contagious skin disease that can have a devastating impact on affected wild mammal populations. There are notable variations in the clinical and pathologic picture of sarcoptic mange among species and among conspecifics. However, the origin of these variations is unclear. We propose a classification scheme for skin lesions associated with Sarcoptes scabiei infestation to provide a basis for a subsequent risk factor analysis. We conducted a case-control study focused on macroscopic and histologic examination of the skin, using 279 red foxes (Vulpes vulpes) found dead or shot in Switzerland between November 2004 and February 2006. All animals were submitted to gross necropsy following a detailed protocol. Selection criteria for cases (n=147) vs. controls (n=111) were the presence or absence of mange-like lesions, mite detection by isolation or histologic examination, and serologic testing for S. scabiei antibodies. Characteristic features of mange lesions were scored macroscopically in all foxes and histologically in 67 cases and 15 controls. We classified skin lesions and associated necropsy findings into three types of mange: A) early stage (n=45): focal-extensive skin lesions, thin crusts, mild to moderate alopecia, few mites, numerous eosinophils, and mild lymph node enlargement; B) hyperkeratotic, fatal form (n=86): generalized skin lesions, thick crusts with or without alopecia, foul odor, abundance of mites, numerous bacteria and yeasts, numerous lymphocytes and mast cells, severe lymph node enlargement, and emaciation; C) alopecic, healing form (n=16): focal lesions, no crusts, severe alopecia, hyperpigmentation and lichenification, absence of mites, mixed cell infiltration, and rare mild lymph node enlargement. We hypothesize that after stage A, the animal either enters stage B and dies, or stage C and survives, depending on largely unknown extrinsic or intrinsic factors affecting the host ability to control mite infestation.

Maternal allocation in bison: co-occurrence of senescence, cost of reproduction, and individual quality

Parental allocation strategies are of profound interest in life history because they directly impact offspring fitness and therefore are highly valuable for understanding population dynamics and informing management decisions. Yet, numerous questions about reproductive allocation patterns for wild populations of large mammals remain unanswered because of the challenges for measuring allocation in the wild. Using a nine-year longitudinal data set on life-history traits of mother–calf bison pairs, we identified sources of variation in relative maternal allocation (calf mass ratio on mother mass) and assessed the occurrence of reproductive costs associated with differential maternal allocation. We found that heavy mothers provided a lower allocation but still produced heavier calves than light mothers. Older females produced lighter calves and tended to decrease allocation as they aged, supporting the occurrence of reproductive senescence. Mothers that had produced a calf the previous year produced lighter calves and allocated less than mothers that did not lactate the previous year, revealing reproductive costs. However, greater maternal allocation did not reduce the probability of breeding in successive years, and the amount of allocation provided by a mother was positively correlated among the offspring she produced, illustrating individual heterogeneity. Although life-history studies are usually classified as either supporting costs of reproduction or individual quality, our study demonstrates that these contrasting evolutionary forces can shape variation within a single trait. Our work illustrates that many processes can coevolve within a population, emphasizing the need to integrate multiple concepts to better understand the evolution of life-history traits. With regard to management of bison herds, if the goal of culling programs is to select for animals with the best performance, this research suggests that managers should account for the condition and previous reproductive status of mothers when taking culling decisions on juvenile bison.

Maternal allocation in bison: co-occurrence of senescence, cost of reproduction, and individual quality

Parental allocation strategies are of profound interest in life history because they directly impact offspring fitness and therefore are highly valuable for understanding population dynamics and informing management decisions. Yet, numerous questions about reproductive allocation patterns for wild populations of large mammals remain unanswered because of the challenges for measuring allocation in the wild. Using a nine-year longitudinal data set on life-history traits of mother-calf bison pairs, we identified sources of variation in relative maternal allocation (calf mass ratio on mother mass) and assessed the occurrence of reproductive costs associated with differential maternal allocation. We found that heavy mothers provided a lower allocation but still produced heavier calves than light mothers. Older females produced lighter calves and tended to decrease allocation as they aged, supporting the occurrence of reproductive senescence. Mothers that had produced a calf the previous year produced lighter calves and allocated less than mothers that did not lactate the previous year, revealing reproductive costs. However, greater maternal allocation did not reduce the probability of breeding in successive years, and the amount of allocation provided by a mother was positively correlated among the offspring she produced, illustrating individual heterogeneity. Although life-history studies are usually classified as either supporting costs of reproduction or individual quality, our study demonstrates that these contrasting evolutionary forces can shape variation within a single trait. Our work illustrates that many processes can coevolve within a population, emphasizing the need to integrate multiple concepts to better understand the evolution of life-history traits. With regard to management of bison herds, if the goal of culling programs is to select for animals with the best performance, this research suggests that managers should account for the condition and previous reproductive status of mothers when taking culling decisions on juvenile bison.

Inbreeding and inbreeding depression of early life traits in a cooperative mammal

Mating between relatives often results in negative fitness consequences or inbreeding depression. However, the expression of inbreeding in populations of wild cooperative mammals and the effects of environmental, maternal and social factors on inbreeding depression in these systems are currently not well understood. This study uses pedigree-based inbreeding coefficients from a long-term study of meerkats (Suricata suricatta) in South Africa to reveal that 44% of the population have detectably non-zero (F > 0) inbreeding coefficients. 15% of these inbred individuals were the result of moderate inbreeding (F ≥ 0.125), although such inbreeding events almost solely occurred when mating individuals had no prior experience of each other. Inbreeding depression was evident for a range of traits: pup mass at emergence from the natal burrow, hind-foot length, growth until independence and juvenile survival. However, we found no evidence of significant inbreeding depression for skull and forearm length or for pup survival. This research provides a rare investigation into inbreeding in a cooperative mammal, revealing high levels of inbreeding, considerable negative consequences and complex interactions with the social environment.

Osteoarthritis in the early avian radiation: Earliest recognition of the disease in birds

Osteoarthritis is extremely rare in wild mammal populations (less than 1%) and varies in frequency according to species (0–25%) in recent birds, where it is inversely related to size. Large population samples of Early Cretaceous birds in China permit us to analyze its frequency in one of the earliest avian radiations. In these samples, the larger bird (Caudipteryx) shows a high frequency (30%). The earliest previous documentation of primary osteoarthritis in any animal is in a family of Early Cretaceous dinosaurs (Iguanodontidae). We document its occurrence in a basal bird and in one of the forms considered by some to be a feathered dinosaur. These occurrences are 20 million years older than the next oldest occurrence of osteoarthritis.

Age‐related variation in immunity in a wild mammal population

SummaryAge-related changes in immunity are well documented in humans and laboratory mammals. Using blood samples collected from wild Soay sheep, we show that pronounced differences in T-cell subsets and inflammatory markers amongst age classes are also evident under natural conditions. These shifts parallel those observed in mammals experiencing protected environments. We found progressive declines in the proportion of naïve CD4 T cells with age, a precipitous drop in γδ T cells after the second year of life and an increase in acute phase protein levels amongst geriatric sheep. Our findings suggest immune aging patterns observed in laboratory and domestic mammals may generalize to more complex, challenging environments and could have fitness costs under natural conditions.

Thermal adaptation in endotherms: climate and phylogeny interact to determine population‐level responses in a wild rat

Summary1. The ecology of endotherms is driven by their great energetic need for thermoregulation, which renders mammals and birds particularly vulnerable to environmental temperature and resource fluctuations. Important outstanding questions are whether populations are specialized to their particular climate, and to what extent gene × environment interactions determine thermal responses.2. Here, we show that phylogenetic relatedness and climate interact to determine metabolic capacities, body temperature and morphology in a wild rat (Rattus fuscipes).3. Mitochondrial metabolic capacities are greater in warm climate populations, indicating that these responses are not the result of cold adaptation. However, glycolytic capacities, fur thickness and capacity for nonshivering thermogenesis are greater in cool climate populations. In populations from cooler climates, body temperatures are lower, but more variable. Together, these changes lead to substantial energy savings in cool climate populations, although all traits are constrained by phylogenetic relatedness.4. We demonstrate for the first time that gene × environment interactions determine thermal responses in wild mammal populations, and we suggest that physiological variability among populations may render the species more resilient to climate change because it increases whole‐species performance breadth. Climate envelope modelling is therefore insufficient to predict the future impact of climate change.

Can unified theories of biodiversity explain mammalian macroecological patterns?

The idea of a unifying theory of biodiversity linking the diverse array of macroecological patterns into a common theoretical framework is very appealing. We explore this idea to examine currently proposed unified theories of biodiversity (UTBs) and their predictions. Synthesizing the literature on the macroecological patterns of mammals, we critically evaluate the evidence to support these theories. We find general qualitative support for the UTBs' predictions within mammals, but rigorous testing is hampered by the types of data typically collected in studies of mammals. In particular, abundance is rarely estimated for entire mammalian communities or of individual species in multiple locations, reflecting the logistical challenges of studying wild mammal populations. By contrast, there are numerous macroecological patterns (especially allometric scaling relationships) that are extremely well characterized for mammals, but which fall outside the scope of current UTBs. We consider how these theories might be extended to explain mammalian biodiversity patterns more generally. Specifically, we suggest that UTBs need to incorporate the dimensions of geographical space, species' traits and time to reconcile theory with pattern.

Identifying Y-chromosomal diversity by long-template PCR

Comparing Y-chromosomal and mitochondrial haplotype variation is a promising approach to independently investigate paternal and maternal evolutionary histories in wild mammal populations. However, the difficulty of developing male-specific genetic markers, because of its distinctive genetic architecture and the general low level of polymorphisms observed on the Y chromosome, hampers usually an effective application of this approach. Here, we present a further method of the established Y chromosome conserved anchored tagged sequences strategy to develop Y-chromosomal markers by screening introns of male-specific region (MSY) genes for sequence polymorphisms. By applying long-template PCR using target species-specific primers, adequate sequence information of several kb in size can be obtained. We applied this method in the snow vole (Chionomys nivalis) and obtained 12.4 kb of male-specific sequence data for nine males representing four populations in the Swiss Alps. A total of 28 single nucleotide polymorphisms, four indels (> 1 bp) and one polymorphic microsatellite were identified in introns of the SMCY and DBY genes. Based on this information, we developed a Y-chromosomal genotyping assay and identified four different paternal lineages within one local snow vole population. The method we present is straightforward and as such will probably be suitable to detect adequate Y-chromosomal diversity in a wide range of mammalian species.

Inbreeding depression in red deer calves

BackgroundUnderstanding the fitness consequences of inbreeding is of major importance for evolutionary and conservation biology. However, there are few studies using pedigree-based estimates of inbreeding or investigating the influence of environment and age variation on inbreeding depression in natural populations. Here we investigated the consequences of variation in inbreeding coefficient for three juvenile traits, birth date, birth weight and first year survival, in a wild population of red deer, considering both calf and mother's inbreeding coefficient. We also tested whether inbreeding depression varied with environmental conditions and maternal age.ResultsWe detected non-zero inbreeding coefficients for 22% of individuals with both parents and at least one grandparent known (increasing to 42% if the dataset was restricted to those with four known grandparents). Inbreeding depression was evident for birth weight and first year survival but not for birth date: the first year survival of offspring with an inbreeding coefficient of 0.25 was reduced by 77% compared to offspring with an inbreeding coefficient of zero. However, it was independent of measures of environmental variation and maternal age. The effect of inbreeding on birth weight appeared to be driven by highly inbred individuals (F = 0.25). On the other hand first year survival showed strong inbreeding depression that was not solely driven by individuals with the highest inbreeding coefficients, corresponding to an estimate of 4.35 lethal equivalents.ConclusionsThese results represent a rare demonstration of inbreeding depression using pedigree-based estimates in a wild mammal population and highlight the potential strength of effects on key components of fitness.

Host taxon-derived Sarcoptes mite in European wild animals revealed by microsatellite markers

Ten markers specific to Sarcoptes mites were used in applying microsatellite genotyping to individual Sarcoptes mites collected in three European countries from 15 wild mammal populations belonging to 10 host species. The results showed that geographical separation had real biological significance for the definition of mite sub-populations, and that the degree of genetic exchange occurring between mites from different localities was apparently related to the geographical distance between locations. Wild host-derived mite populations were found to be clustered into three main groups: herbivore-, carnivore- and omnivore-derived Sarcoptes populations, with the omnivore-derived group located halfway between the herbivore- and carnivore-derived Sarcoptes populations. The separation between these three mite groups was better supported than the geographical separations; nevertheless, a kind of sub-clustering was detected within each of these three groups that separates mite populations into their geographical localities (countries). The lack of gene flow between Sarcoptes populations may have improved parasitic adaptations and led to what we refer to as a host-taxon-derived (carnivore host-, herbivore host- and omnivore host-derived) Sarcoptes mite found on European wild animals. Our results demonstrate that Sarcoptes is not a single panmictic population, even within each geographical location. This finding will have important ramifications for the study of the genetic structure of populations, life cycles, diagnosis and the monitoring protocols of the ubiquitous Sarcoptes mite, and could thus contribute to a better understanding of its associated epidemiology, which is of pivotal interest for wildlife biological conservation.

Achieving success with small, translocated mammal populations

AbstractTranslocations are increasingly important tools for endangered species conservation, but their success is often uncertain. We analyzed 125 time series of grazing mammal translocations in South African protected areas. Some 94% of translocations succeeded (66% unambiguously) even though most populations began with <15 individuals and most of the species involved are of conservation concern. Adding new individuals to existing small populations increases per capita growth rates and seems to prevent translocations from failing. Growth of the translocated populations is both greater and less variable than wild mammal populations and appears less affected by the typically important ecological factors (e.g., initial propagule size, precipitation, reserve size, or presence within historical range). One‐third of the populations showed robust signs of density dependence but we detect few examples of Allee effects. Our results, from empirical time series of small populations, offer new insights into achieving success for translocation programs limited to releasing few individuals.

Who infects whom? Social networks and tuberculosis transmission in wild meerkats

Transmission of infectious diseases is strongly influenced by who contacts whom. Despite the global distribution of tuberculosis (TB) in free-living wild mammal populations, little is known of the mechanisms of social transmission of Mycobacterium bovis between individuals. Here, I use a network approach to examine for correlations between five distinct types of intra- and intergroup social interaction and changes in TB status of 110 wild meerkats (Suricata suricatta) in five social groups over two years. Contrary to predictions, the most socially interactive animals were not at highest risk of acquiring infection, indicating that in addition to contact frequency, the type and direction of interactions must be considered when quantifying disease risk. Within social groups, meerkats that groomed others most were more likely to become infected than individuals who received high levels of grooming. Conversely, receiving, but not initiating, aggression was associated with M. bovis infection. Incidence of intergroup roving by male meerkats was correlated with the rovers themselves subsequently testing TB-positive, suggesting a possible route for transmission of infection between social groups. Exposure time was less important than these social interactions in influencing TB risk. This study represents a novel application of social network analysis using empirical data to elucidate the role of specific interactions in the transmission of an infectious disease in a free-living wild animal population.

Antimicrobial-resistant faecalEscherichia coliin wild mammals in central Europe: multiresistantEscherichia coliproducing extended-spectrum beta-lactamases in wild boars

To determine the presence of antibiotic-resistant faecal Escherichia coli in populations of wild mammals in the Czech Republic and Slovakia. Rectal swabs or faeces collected during 2006-2008 from wild mammals were spread on MacConkey agar and MacConkey agar containing 2 mg l(-1) of cefotaxime. From plates with positive growth, one isolate was recovered and identified as E. coli. Susceptibility to 12 antibiotics was tested using the disk diffusion method. Resistance genes, class 1 and 2 integrons and gene cassettes were detected in resistant isolates by polymerase chain reaction (PCR). Extended-spectrum beta-lactamases (ESBL) were further characterized by DNA sequencing, macrorestriction profiling and determination of plasmid sizes. Plasmid DNA was subjected to EcoRV digestion, transferability by conjugation and incompatibility grouping by multiplex PCR. The prevalence of resistant isolates was 2% in small terrestrial mammals (rodents and insectivores, n(E. coli) = 242), 12% in wild ruminants and foxes (n(E. coli) = 42), while no resistant isolates were detected in brown bears (n(E. coli) = 16). In wild boars (Sus scrofa) (n(E. coli) = 290), the prevalence of resistant isolates was 6%. Class 1 and 2 integrons with various gene cassettes were recorded in resistant isolates. From wild boars, five (2%, n(rectal smears) = 293) multiresistant isolates producing ESBL were recovered: one isolate with bla(CTX-M-1) + bla(TEM-1), three with bla(CTX-M-1) and one with bla(TEM-52b). The bla(CTX-M-1) genes were carried on approx. 90 kb IncI1 conjugative plasmids. Antibiotic-resistant E. coli occurred in populations of wild mammals in various prevalences. Wild mammals are reservoirs of antibiotic-resistant E. coli including ESBL-producing strains which were found in wild boars.

Morphology and Occurrence of Species of Toxocara in Wild Mammal Populations from Egypt

Abstract Toxocara spp. are zoonotic helminths of domestic and wild mammals and have been implicated in serious human disease. The present study was undertaken to differentiate among various adult Toxocara spp. infecting some wild and stray mammals and to evaluate the frequency of infection by Toxocara in wild mammals that may serve as a potential source of Toxocara infection in humans. Infection by adult Toxocara canis (Warner, 1782) was found in 31 of 58 (53.4%) domestic dogs (Canis lupus familiaris), 20 of 41 (48.8%) red foxes (Vulpes vulpes), 27 of 43 (62.8%) grey wolves (Canis lupus); and 25 of 42 (59.5%) Egyptian mongooses (Herpestes ichneumon); the grey wolf and the Egyptian mongoose are new host records for Egypt. Toxocara cati (Schrank, 1788) Brumpt, 1927, was found in 27 of 46 (58.7%) wild cats (Felis sylvestris). The mean intensity and abundance of T. canis was highest in grey wolves and lowest in red foxes. The prevalence, intensity, and abundance varied with host species, sex, and season. Prev...

The magnitude and selectivity of natural and multiple anthropogenic mortality causes in hunted brown bears

1. The population dynamic and evolutionary effects of harvesting are receiving growing attention among biologists. Cause-specific estimates of mortality are necessary to determine and compare the magnitude and selectivity of hunting and other types of mortalities. In addition to the logistic and financial constraints on longitudinal studies, they are complicated by the fact that nonhunting mortality in managed populations usually consists of a mix of natural and human-caused factors. 2. We used multistate capture-recapture (MCR) models to estimate cause-specific survival of brown bears (Ursus arctos) in two subpopulations in Sweden over a 23-year period. In our analysis, we distinguished between legal hunting and other sources of mortality, such as intraspecific predation, accidents, poaching, and damage control removals. We also tested whether a strong increase in harvest quotas after 1997 in one of the subpopulations affected vulnerability to legal hunting. 3. Although only a fraction of mortalities other than legal hunting could be considered natural, this group of causes showed a general pattern of demographic selectivity expected from natural mortality regimes in populations of long-lived species, namely greater vulnerability of young animals. On the other hand, demographic effects on hunting vulnerability were weak and inconsistent. Our findings support the assumption that hunting and other mortalities were additive. 4. As expected, an increase in hunting pressure coincided with a correspondingly large increase in vulnerability to hunting in the affected subpopulation. Because even unbiased harvest can lead to selective pressures on life-history traits, such as size at primiparity, increasing harvest quotas may not only affect population growth directly, but could also alter optimal life-history strategies in brown bears and other carnivores. 5. Legal hunting is the most conveniently assessed and the most easily managed cause of mortality in many wild populations of large mammals. Although legal hunting is the single-most important cause of mortality for brown bears in Sweden, the combined mortality from other causes is of considerable magnitude and additionally shows greater selectivity in terms of sex and age than legal hunting. Therefore, its role in population dynamics and evolution should not be underestimated.

A scoring system for coat and tail condition in ringtailed lemurs, Lemur catta

Coat condition can be influenced by a wide variety of disorders and thus provides a useful tool for noninvasive health and welfare assessments in wild and captive animals. Using Lemur catta as an exemplar, we offer a 6-step scoring system for coat and tail condition, ranging from perfectly fluffy to half or more of body and tail being hairless. The categories are described in detail and illustrated with sample pictures from a wild population in Berenty Reserve, Madagascar. Furthermore, we elaborate on intermediate conditions and discoloration of fur. Coat condition scoring allows the comparison between years, seasons, and the effect of toxin, disease or stress. Although this system was developed for wild L. catta, we believe it can also be of value for other species. We recommend scoring coat condition in healthy wild mammal populations to give a baseline on yearly and seasonal variations vs. deteriorating health conditions or pathology.

Age- and sex-specific settlement patterns of chamois (Rupicapra rupicapra) offspring

The social, spatial, and genetic structures of populations depend on where offspring settle and reproduce in relation to their parent’s home range. However, the patterns of settlement in wild populations of large mammals are often poorly described owing to the difficulty of monitoring mother–offspring pairs over a long period. Here, we investigated sex-specific settlement patterns in chamois ( Rupicapra rupicapra (L., 1758)) based on the study of 31 mother–offspring pairs. We calculated the distance between the center of the mother’s range and the center of her offspring’s range, and tested whether this distance differed when the offspring was immature (i.e., a yearling) and after offspring sexual maturity (>2 years of age). We found no sex effect on the distance between centers of mother and offspring ranges for yearling offsprings. However, mature sons ranged farther away from their mother than mature daughters. Daughters appear to settle close to their mother’s home range. The distance at which a daughter settles compared with her mother’s range seems to be determined before 2 years of age. On the contrary, the distance between the center of the locations of yearling males and the center of locations of their mother does not predict how far away males will eventually settle when mature. We discuss the implications of these patterns for generating female social structures, as well as population spatial and genetic structures.

Compendium of Animal Rabies Prevention and Control, 2008

sive encephalitis caused by a Lyssavirus. Although the United States has been declared free of canine rabies virus variant transmission, multiple viral variants are maintained in wild mammal populations, and there is always a risk of reintroduction of canine rabies. 2 All mammals are believed to be susceptible to the disease, and for purposes of this document, use of the term animal refers to mammals. The recommendations in this compendium serve as a basis for animal rabies-prevention and -control programs throughout the United States and facilitate standardization of procedures among jurisdictions, thereby contributing to an effective national rabies-control program. This document is reviewed annually and revised as necessary, and the most current version replaces all previous versions. These recommendations do not supersede state and local laws or requirements. Principles of rabies prevention and control are detailed in Part I; Part II contains recommendations for parenteral vaccination procedures; all animal rabies vaccines licensed by the USDA and marketed in the United States are listed in Part III.