151 research outputs found
Early-life adversity predicts performance and fitness in a wild social carnivore
1. Studies on humans indicate that encountering multiple sources of adversity in childhood increases the risk of poor long-term health and premature death. Far less is known about cumulative effects of adversity during early life in wildlife.
2. Focusing on the spotted hyena Crocuta crocuta, a social mammal with small litters, extensive maternal care, slow development and access to resources determined by social rank, we determined the contribution of ecological, maternal, social and demographic factors during early life on performance and fitness, and tested whether the impact of early-life adversity is cumulative.
3. Using longitudinal data from 666 female hyenas in the Serengeti National Park, we determined the early growth rate, survival to adulthood, age at first reproduction (AFR), lifetime reproductive success (LRS) and longevity. We fitted multivariate models in which we tested the effects of environmental factors on these performance measures. We then constructed a cumulative adversity index and fitted models to test the effect of this index on each performance measure. Finally, the value of cumulative adversity models was tested by comparing them to multivariate and single-effect models in which the effect of each environmental factor was considered separately.
4. High maternal rank decreased the AFR of daughters. Singleton and dominant cubs had higher growth rate than subordinate cubs, and singletons also had a higher survival chance to adulthood than subordinates. Daughters of prime age mothers had a higher growth rate, longevity and LRS. Little and heavy rainfall decreased survival to adulthood. Increasing numbers of lactating female clan members decreased growth rate, survival to adulthood and LRS. Cumulative adversity negatively affected short-term performance and LRS. Multivariate models outperformed cumulative adversity and single-effect models for all measures except for AFR and longevity, for which single-effect models performed better.
5. Our results suggest that in some wildlife populations the combination of specific conditions in early life may matter more than the accumulation of adverse conditions as such
Characterization of spotted hyena, Crocuta crocuta microsatellite loci
We have isolated 10 polymorphic microsatellite loci in the spotted hyena,Crocuta crocuta.The loci displayed between eight and 14 alleles in a minimum of 12 individuals tested.
These loci will be used to investigate relatedness within social groups, the genetic structure of populations, sexual selection, and mate choice in spotted hyenas
Climate change does not decouple interactions between a central-place-foraging predator and its migratory prey
Little is known about potential cascading effects of climate change on the ability of predators to exploit mobile aggregations of prey with a spatiotemporal distribution largely determined by climatic conditions. If predators employ central-place foraging when rearing offspring, the ability of parents to locate sufficient prey could be reduced by climate change. In the Serengeti National Park, Tanzania, migratory species dominate mammalian herbivore biomass. These migratory herds exploit nutrient-rich vegetation on the southern plains in the rainy season and surface water in the northwest in the dry season. Female spotted hyenas Crocuta crocuta breed throughout the year and use long-distance central-place-foraging “commuting trips” to migratory herds to fuel lactation for ≥12 months. Changes in rainfall patterns that alter prey movements may decrease the ability of mothers to locate profitable foraging areas and thus increase their overall commuting effort, particularly for high-ranking females that have priority of access to food resources within their clan territory and thus less commuting experience. In hyena clan territories, this may be reflected by a decrease in migratory herd presence and a decrease in the presence of lactating females, as maternal den presence represents the opposite of commuting effort. We investigated the strength of the relationship between rainfall volume, migratory herd presence in three hyena clan territories, and the responses of lactating females to this climate/prey relationship in terms of maternal den presence, using an observation-based dataset spanning three decades. The probability of migratory herd presence in hyena clan territories increased with the amount of rainfall 2 months earlier, and maternal den presence increased with migratory herd presence. Rainfall volume substantially increased over 30 years, whereas the presence of migratory herds in hyena clans and the strength of the relationship between rainfall and migratory herd presence decreased. Hyenas thus adjusted well to the climate change-induced decreased the presence of migratory herds in their territories, since maternal den presence did not decrease over 30 years and still matched periods of high prey abundance, irrespective of female social status. These results suggest a high plasticity in the response of this keystone predator to environmental variability
Diet of the Golden Jackal (Canis aureus) and Silver-Backed Jackal (Canis mesomelas) in the Southern Part of the Serengeti Ecosystem, Tanzania: A Comparative Study
Habitat and food resource partitioning are predicted to facilitate the coexistence of similar-sized carnivores. The golden jackal (Canis aureus) and silver-backed jackal (Canis mesomelas) are similar-sized canids that respectively inhabit grassland and woodland in the Serengeti ecosystem, Tanzania. As information on the diet and food-intake of these two species in this ecosystem is limited, we aimed to compare the diet and food-intake of these canids in the wet and dry seasons, using data from focal samples of foraging behaviour and scat analysis. We predicted dietary differences between these species, seasonal differences within species and peak food intake when breeding. Result of a logistic regression considering insect and small mammal remains in scats revealed dietary differences both between species and within-species seasonal differences. Results of a censored regression model on the estimated weigh of food intake by foraging individuals indicated that intake was highest during the breeding season of each species, which occurs in the wet season in golden jackals and the dry-season in silver-backed jackals. Our study provides new insights on differences in the foraging ecology of these two jackal species in the Serengeti ecosystem.
Keywords: Canis aureus; Canis mesomelas, diet, Serengeti ecosystem, season
Epigenetic signatures of social status in wild female spotted hyenas (Crocuta crocuta)
In mammalian societies, dominance hierarchies translate into inequalities in health, reproductive performance and survival. DNA methylation is thought to mediate the effects of social status on gene expression and phenotypic outcomes, yet a study of social status-specific DNA methylation profiles in different age classes in a wild social mammal is missing. We tested for social status signatures in DNA methylation profiles in wild female spotted hyenas (Crocuta crocuta), cubs and adults, using non-invasively collected gut epithelium samples. In spotted hyena clans, female social status influences access to resources, foraging behavior, health, reproductive performance and survival. We identified 149 differentially methylated regions between 42 high- and low-ranking female spotted hyenas (cubs and adults). Differentially methylated genes were associated with energy conversion, immune function, glutamate receptor signalling and ion transport. Our results provide evidence that socio-environmental inequalities are reflected at the molecular level in cubs and adults in a wild social mammal
11-2001 Newsletter
Minnesota State University, Mankato, Library Services Newsletter for November 2001
Genetic Diversity, Latency and Co-Infections
Alphaherpesviruses are highly prevalent in equine populations and co-
infections with more than one of these viruses’ strains frequently diagnosed.
Lytic replication and latency with subsequent reactivation, along with new
episodes of disease, can be influenced by genetic diversity generated by
spontaneous mutation and recombination. Latency enhances virus survival by
providing an epidemiological strategy for long-term maintenance of divergent
strains in animal populations. The alphaherpesviruses equine herpesvirus 1
(EHV-1) and 9 (EHV-9) have recently been shown to cross species barriers,
including a recombinant EHV-1 observed in fatal infections of a polar bear and
Asian rhinoceros. Little is known about the latency and genetic diversity of
EHV-1 and EHV-9, especially among zoo and wild equids. Here, we report
evidence of limited genetic diversity in EHV-9 in zebras, whereas there is
substantial genetic variability in EHV-1. We demonstrate that zebras can be
lytically and latently infected with both viruses concurrently. Such a co-
occurrence of infection in zebras suggests that even relatively slow-evolving
viruses such as equine herpesviruses have the potential to diversify rapidly
by recombination. This has potential consequences for the diagnosis of these
viruses and their management in wild and captive equid populations. View Full-
Tex
Comprehensive Serology Based on a Peptide ELISA to Assess the Prevalence of Closely Related Equine Herpesviruses in Zoo and Wild Animals
Equine herpesvirus type 1 (EHV-1) causes respiratory disorders and abortion in
equids while EHV-1 regularly causes equine herpesvirus myeloencephalopathy
(EHM), a stroke-like syndrome following endothelial cell infection in horses.
Both EHV-1 and EHV-9 infections of non-definitive hosts often result in
neuronal infection and high case fatality rates. Hence, EHV-1 and EHV-9 are
somewhat unusual herpesviruses and lack strict host specificity, and the true
extent of their host ranges have remained unclear. In order to determine the
seroprevalence of EHV-1 and EHV-9, a sensitive and specific peptide-based
ELISA was developed and applied to 428 sera from captive and wild animals
representing 30 species in 12 families and five orders. Members of the
Equidae, Rhinocerotidae and Bovidae were serologically positive for EHV-1 and
EHV-9. The prevalence of EHV-1 in the sampled wild zebra populations was
significantly higher than in zoos suggesting captivity may reduce exposure to
EHV-1. Furthermore, the seroprevalence for EHV-1 was significantly higher than
for EHV-9 in zebras. In contrast, EHV-9 antibody prevalence was high in
captive and wild African rhinoceros species suggesting that they may serve as
a reservoir or natural host for EHV-9. Thus, EHV-1 and EHV-9 have a broad host
range favoring African herbivores and may have acquired novel natural hosts in
ecosystems where wild equids are common and are in close contact with other
perissodactyls
Measuring faecal epi-androsterone as an indicator of gonadal activity in spotted hyenas (Crocuta crocuta)
Enzyme immunoassays (EIA) that measure faecal testosterone metabolites (fTM) are useful
tools to monitor gonadal activity. The aim of this study was to validate an “in-house”
epiandrosterone EIA to monitor fTM in spotted hyenas. FTM were characterised in a male
and a female hyena that each received an injection of 3H-testosterone. High-performance
liquid chromatography (HPLC) analyses revealed a cluster of highly polar enzyme-hydrolysable
hormone metabolite conjugates. We performed hydrolysis using β-glucuronidase to
deconjugate metabolites and improve sensitivity of the assay. Because β-glucuronidase
from Helix pomatia has been reported to bias testosterone measurements in some species,
we compared the enzymatic activity of the commonly used β-glucuronidase extracted from
H. pomatia with the same enzyme from Escherichia coli. Our results showed that β-glucuronidases
from both sources produced similar results from spotted hyena faeces. We therefore
hydrolysed samples with H. pomatia enzymes. HPLC analyses also demonstrated that
following hydrolysis the epiandrosterone EIA measured significant amounts of immunoreactive
metabolites corresponding to radiolabelled metabolites in both sexes. Additionally,
HPLC and GC-MS analyses confirmed the presence of epiandrosterone in faeces of spotted
hyenas. The biological relevance of the epiandrosterone EIA was validated by demonstrating
(1) a significant increase in fTM levels in response to a testosterone injection within
16 h, (2) no biological responsiveness to an adrenocorticotropic hormone (ACTH) injection
and (3) significant differences in fTM levels between juvenile males and adult immigrant
males in a free-ranging wild population. Our results clearly demonstrate that the epiandrosterone
EIA is a reliable non-invasive method to monitor gonadal activity in spotted hyenas.Funded by a joint
“Collaboration in the field of sustainable management
of wildlife populations” grant (SUA 10/020) of the
International Bureau of the German Federal Ministry
for Education and Research (BMBF) and the National
Research Council of South Africa, and the Leibniz
Institute for Zoo & Wildlife Research (IZW).http://www.plosone.orgam201
Seasonal host and ecological drivers may promote restricted water as a viral vector
In climates with seasonally limited precipitation, terrestrial animals congregate at high densities at scarce
water sources. We hypothesize that viruses can exploit the recurrence of these diverse animal congrega-
tions to spread. In this study, we test the central prediction of this hypothesis — that viruses employing
this transmission strategy remain stable and infectious in water. Equid herpesviruses (EHVs) were cho-
sen as a model as they have been shown to remain stable and infectious in water for weeks under labo-
ratory conditions. Using fecal data from wild equids from a previous study, we establish that EHVs are
shed more frequently by their hosts during the dry season, increasing the probability of water source
contamination with EHV. We document the presence of several strains of EHVs present in high genome
copy number from the surface water and sediments of waterholes sampled across a variety of mamma-
lian assemblages, locations, temperatures and pH. Phylogenetic analysis reveals that the different EHV
strains found exhibit little divergence despite representing ancient lineages. We employed molecular
approaches to show that EHVs shed remain stable in waterholes with detection decreasing with increas-
ing temperature in sediments. Infectivity experiments using cell culture reveals that EHVs remain
infectious in water derived from waterholes. The results are supportive of water as an abiotic viral vector
for EHVacceptedVersio
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