Cyclic changes in cortisol across the estrous cycle in parous and nulliparous Asian elephants

 In the context of reproduction, glucocorticoids (GCs) are generally considered to have negative effects. However, in well-studied model species, GCs fluctuate predictability across the estrous cycles, and short-term increases promote healthy ovarian function. Reproductive challenges have plagued captive elephant populations, which are not currently self-sustaining. Efforts to understand reproductive dysfunction in elephants have focused on the suppressive effects of cortisol, but the potential permissive or stimulatory effects of cortisol are unknown. In this study, we provide a detailed examination of cortisol patterns across the estrous cycle in Asian elephants (Elephas maximus). Time series analysis was used to analyze cortisol and progesterone data for a total of 73 cycles from eight females. We also compared cortisol profiles between females that successfully conceived and females that failed to conceive despite repeated mating attempts. Our results revealed that cortisol fluctuates predictably across the estrous cycle, with a peak during the second half of the follicular phase followed by low levels throughout the luteal phase. Furthermore, this pattern was significantly altered in nulliparous females; cortisol concentrations did not decline during the luteal phase to the same extent as in parous females. This study highlights the complexity of cortisol signaling and suggests future directions for understanding the role of cortisol in reproductive dysfunction

Using path analysis to explore vigilance behavior in the rock hyrax (Procavia capensis)

Group size and vigilance are tools that animals can use to mitigate predation risk, and many studies have reported a negative relationship between them. Vigilance studies often investigate the direct effect of group size on vigilance, but they ignore the effect of ecological factors on group size. As a consequence, these studies can overlook important indirect effects of ecological factors on vigilance via group size. We investigated how ecological factors affect vigilance behavior in rock hyraxes (Procavia capensis), both directly and indirectly via group size. First, we showed a direct negative relationship between group size and vigilance behavior by measuring vigilance behavior before and after a change in group size. Second, we conducted a path analysis that included group size and several ecological factors (distance from shelter, distance from center of kopje, vegetation cover, and time since start of foraging session). Similar to the 1st analysis, the path analysis identified a strong negative relationship between group size and vigilance behavior; however, the other variables had little effect on group size or vigilance behavior, or both.8 page(s

Ecological factors affecting the foraging behaviour of Xerus rutilus

The African unstriped ground squirrel (Xerus rutilus) is widely dispersed across various habitats in East Africa and hence encounters a diverse suite of predators and plant communities. It is not known how different habitats and plant characteristics affect the foraging behaviour of X. rutilus. We used giving-up densities (GUDs) as a measure of foraging efficiency to explore the foraging costs of environmental heterogeneity. To determine foraging efficiency across spatial scales, we established food patches in two microhabitats (open and cover), which were nested within three habitats (koppie, edge and bushland). When foraging in a cover microhabitat, foraging efficiency decreased away from the koppie, but when in the open microhabitat, foraging efficiency was lowest near the koppie edge. Second, to determine foraging efficiency with common plant toxins, we presented the squirrels with seeds soaked in either tannic acid, oxalic acid or distilled water (control). Foraging efficiency did not differ between tannic-treated and control seeds, but oxalic-treated seeds had higher GUDs. Overall, our results suggest that X. rutilus is a remarkably efficient forager across multiple axes of environmental heterogeneity, which may have intriguing consequences for the ecological community.<br /

The effect of behind-the-scenes encounters and interactive presentations on the welfare of captive servals (Leptailurus serval)

The serval (Leptailurus serval) is a small African felid that is well represented in zoos and often serves as an animal ambassador in encounter programs with zoo visitors. The impact on serval welfare in relation to such programs has not been investigated to date, and the aim of this study was to assess short-term welfare effects of varying levels of visitor interaction in two captive servals. Weekly blocks of four different treatments were imposed three times on each animal over 12 weeks, and the treatments involved (1) Presentations (serval undertaking a routine training session in a designated presentation space, typically attracting high visitor numbers), (2) Behind-the-scenes (BTS, a close encounter allowing a small group of visitors to interact closely with the cat in its enclosure), (3) Presentations and BTS combined, and (4) No visitor interaction. Serval activity budgets as well as behavioural diversity were created from behaviours observed from Close Circuit Television (CCTV) footage during four daily recording sessions per animal over three consecutive days per treatment, using instantaneous scan sampling every 60 s. Individual faecal samples were collected daily to monitor changes in faecal glucocorticoid metabolite (FGM) concentration. Results indicate that the mean number of scans with stereotypic pacing was significantly reduced (p = 0.01) during Treatments 1 and 3, when cats participated in presentations only, or the two activities combined. Conversely, a significant reduction in behavioural diversity (p 0.05). Given the reduction in stereotypic pacing, these findings suggest that involvement in an encounter program appears to exert an overall positive short-term welfare effect on the individual servals in this study. Although a reduction in behavioural diversity was not considered a negative welfare effect in the short term, potential long-term negative welfare effects resulting from a more frequent encounter program could not be ruled out in the present study

Foraging behaviour of two rodent species inhabiting a kopje (rocky outcrop) in Tsavo West National Park, Kenya

We employed patch use theory to evaluate how several environmental factors influence the foraging behaviour of two rodent species: Grammomys dolichurus and Acomys cahirinus. Foraging efficiency was determined by measuring the remaining food in artificial food patches (giving-up densities: GUDs) from two experiments. In the first experiment, we placed patches in different microhabitat types (cover vs open) and at varying distances from cover. This experiment was conducted during three moon stages (waxing, full, waning). We found that the rodents had higher GUDs (lower foraging efficiency) in the open microhabitat. The distance from nearest shelter had a marginally significant positive effect on GUDs. GUDs were higher in both microhabitat types during the waxing and full phases, but decreased sharply once the moon began to rise after sunset. These results are likely due to higher predation risk away from cover and in more illuminated environments. In the second experiment, we examined mouse responses to seeds impregnated with plant toxins. Seeds impregnated with oxalic acid were avoided by the rodents, while seeds soaked in tannic acid did not differ significantly from control seeds. Our results highlight important ecological factors affecting the foraging behaviour of these rodents.<br /

Stress and reproductive physiology in Canada lynx (Lynx canadensis): Implications for in-situ and ex-situ conservation

Species reintroductions are a valuable conservation tool, but such efforts often fail, and we have a poor understanding of why. Understanding the role of stress physiology in reintroductions may be critical for enhancing their success rates. The goal of my dissertation was to validate a technique for monitoring stress and reproductive physiology in Canada lynx, and apply this technique to a reintroduced lynx population. The non-invasive technique of fecal hormone analysis was used to accomplish four objectives: (1) investigate the effect of environmental and methodological factors on the quantification of fecal steroid metabolite concentrations, (2) establish normative patterns of male and female reproductive physiology in captive and wild lynx populations, (3) describe patterns of stress physiology in captive and wild lynx populations, and (4) examine changes in stress physiology of lynx throughout the reintroduction process, and investigate patterns of individual variation in stress responses. Validation experiments indicated that fecal steroid metabolites remain relatively stable in winter field conditions, even when exposed to repeated freezing and thawing. Thus biologically meaningful results can be obtained from fecal samples collected in the field. Canada lynx are highly seasonal breeders, and I found that both males and females exhibit seasonal increases in reproductive hormones (estrogens and androgens, respectively), which coincide with the breeding season. Progestogens, which are typically useful for monitoring pregnancy, were not useful indicators of pregnancy in Canada lynx. Nonetheless, they may accurately reflect luteal activity, as corpora lutea in Lynx species may persist for some time, although the dynamics of luteal activity are still poorly understood. Canada lynx are solitary in the wild, and group-housing in captivity appears to alter both reproductive and stress physiology. Population comparisons revealed that captive lynx exhibit higher concentrations of all four steroid hormones than wild populations, which may be linked to differences in energy regulation or metabolism. Finally, in reintroduced lynx, the magnitude of a lynx’ stress response is a significant predictor of post-release survival; lynx with larger stress responses have shorter post-release survival. Thus, fecal hormone analysis provides a valuable tool for monitoring the reproductive and stress physiology of Canada lynx. Furthermore, information gained using this technique can be used to guide the development of stronger management plans for captive and wild populations, thereby improving animal well-being and conservation

Data from: Cost of reproduction in the Queensland fruit fly: Y-model vs. lethal protein hypothesis

The trade-off between lifespan and reproduction is commonly explained by differential allocation of limited resources. Recent research has shown that the ratio of protein to carbohydrate (P:C) of a fly's diet mediates the lifespan/reproduction trade-off, with higher P:C diets increasing egg production but decreasing lifespan. To test if this P:C effect is due to changing allocation strategies (Y-model hypothesis) or detrimental effects of protein ingestion on lifespan (lethal protein hypothesis), we measured lifespan and egg production in Queensland fruit flies varying in reproductive status (mated, virgin, and sterilized females, virgin males) that were fed one of 18 diets varying in protein and carbohydrate amounts. The Y-model predicts that for sterilized females and for males, which require little protein for reproduction, there will be no effect of P:C ratio on lifespan; the lethal protein hypothesis predicts that the effect of P:C ratio should be similar in all groups. In support of the lethal protein hypothesis, and counter to the Y model, the P:C ratio of the ingested diets had similar effects for all groups. We conclude that the trade-off between lifespan and reproduction is mediated by the detrimental side-effects of protein ingestion on lifespan

Foraging behaviour of two rodent species inhabiting a kopje (rocky outcrop) in Tsavo West National Park, Kenya

We employed patch use theory to evaluate how several environmental factors influence the foraging behaviour of two rodent species: Grammomys dolichurus and Acomys cahirinus. Foraging efficiency was determined by measuring the remaining food in artificial food patches (giving-up densities: GUDs) from two experiments. In the first experiment, we placed patches in different microhabitat types (cover vs open) and at varying distances from cover. This experiment was conducted during three moon stages (waxing, full, waning).We found that the rodents had higher GUDs (lower foraging efficiency) in the open microhabitat. The distance from nearest shelter had a marginally significant positive effect on GUDs. GUDs were higher in both microhabitat types during the waxing and full phases, but decreased sharply once the moon began to rise after sunset. These results are likely due to higher predation risk away from cover and in more illuminated environments. In the second experiment, we examined mouse responses to seeds impregnated with plant toxins. Seeds impregnated with oxalic acid were avoided by the rodents, while seeds soaked in tannic acid did not differ significantly from control seeds. Our results highlight important ecological factors affecting the foraging behaviour of these rodents.Key words: giving-up densities, foraging ecology, kopje, lunar