Testosterone increase in free-living young Blackcaps <i>Sylvia atricapilla</i> and Wood Warblers <i>Phylloscopus sibilatrix</i> during post-juvenile molt with possible implications for juvenile dispersal

Testosterone may affect many aspects of passerine maturation including the expression of plumage coloration and spring migration in adult birds. However, how the testosterone level changes during bird development is not well known. We compared the testosterone profile during juvenile development of a sexually dimorphic species, the Blackcap Sylvia atricapilla, and a monomorphic species, the Wood Warbler Phylloscopus sibilatrix. We first tested whether testosterone influences plumage coloration and increases at the onset of molt in males of the dimorphic but not the monomorphic species. We found that a testosterone level increase occurred in both sexes and species during later stages of molt, and thus was not related to male plumage coloration. We also investigated whether the increase in testosterone level coincides with juvenile dispersal. If testosterone affects dispersal behavior in these species, both sexes should show an elevated testosterone level during dispersal, but this increase should occur earlier in the Wood Warbler, which disperses earlier than the Blackcap. In juvenile Blackcaps, the increase in testosterone level occurred on the 43-68th day after hatching, while in Wood Warblers it occurred on the 32-36th day (i.e. 11-32 days earlier). The increase in testosterone level coincided with the onset of the post-juvenile dispersal in both species. This study provides the first direct evidence of a testosterone level increase during juvenile development in two free-living migratory birds. While not correlated with species plumage coloration, this increase might affect other aspects of behavior, e.g. juvenile dispersal

Serum prevalence to non-viral pathogens in wild felids of Southern Primorye, Russia

Serum prevalence to six different non-viral pathogens was estimated for big Russian cats (Amur tiger (Panthera tigris altaica) and the Far Eastern leopard (Panthera pardus orientalis)) in Southern Primorye, Russia (n = 26) in 2008–2016. Serum samples from smaller cats (Eurasian lynx (Lynx lynx) and Far Eastern wildcat (Prionailurus bengalensis euptilurus)) were also tested for these pathogens (n = 28) during the same period. Felids of Russian Southern Primorye showed serum prevalence to five out of six tested pathogens. Antibodies to Candida sp. and Trichinella sp. were found to be much more widespread in cats (47% and 42%) than antibodies to other tested pathogens (20% and less). Large cats demonstrated a higher serum prevalence to these pathogens than smaller ones. We did not detect animals seropositive to Coxiella burnetii

Distemper, extinction, and vaccination of the Amur tiger

Canine distemper virus (CDV) has recently emerged as an extinction threat for the endangered Amur tiger (Panthera tigris altaica). CDV is vaccine-preventable, and control strategies could require vaccination of domestic dogs and/or wildlife populations. However, vaccination of endangered wildlife remains controversial, which has led to a focus on interventions in domestic dogs, often assumed to be the source of infection. Effective decision making requires an understanding of the true reservoir dynamics, which poses substantial challenges in remote areas with diverse host communities. We carried out serological, demographic, and phylogenetic studies of dog and wildlife populations in the Russian Far East to show that a number of wildlife species are more important than dogs, both in maintaining CDV and as sources of infection for tigers. Critically, therefore, because CDV circulates among multiple wildlife sources, dog vaccination alone would not be effective at protecting tigers. We show, however, that low-coverage vaccination of tigers themselves is feasible and would produce substantive reductions in extinction risks. Vaccination of endangered wildlife provides a valuable component of conservation strategies for endangered species

Predator presence affects the reproductive success of prey in outdoor conditions

The reproductive outcomes of laboratory rats (Rattus norvegicus) housed at different distances (2, 20 and 80 m) from a predator (Lynx lynx) were investigated. Virgin female (n = 120) and m3ie (n = 40) rats of an outbred laboratory population were used for the experiments. Groups of rats (one male and three females) were housed in standard cages in close proximity to the predator Litter size, sex ratio. number of live pups, number of placental scars and corpora lurea were counted; and pre- and post-implantation losses were calculated for each female. The reproductive success of females, estimated as the number of live pups per female, was significantly higher in both control groups (20 and 80 m) than in both experimental Eraups (2 and 2 m). Equal numbers of corpora lutea in all groups but different numbers of placental scars between control and experimental groups indicated higher pre-implantation losses in the experimental groups. Post-implantation losses were also higher in both experimental groups. Total losses (calculated as a difference between the number of corpora lutea and live pups) were twice as high in experimental groups. Reproductive success of rats depended on concentrate/intensity of predator scents: when concentration/intensity was higher, the number of live pups was less and the total loss was higher

Migratory Species Show Distinct Patterns in Corticosterone Levels during Spring and Autumn Migrations

Twice a year billions of birds migrate between breeding and wintering grounds. To facilitate migrations, birds develop migratory disposition, a complex suite of behavioral and physiological adjustments. Glucocorticoid hormone corticosterone is involved in the regulation of migratory behavior and physiology, however no consensus on its exact role in controlling avian migration exists. Using a large dataset on seven songbird species (long- and short-distance migrants) obtained during eleven consecutive migratory seasons on the Courish Spit of the Baltic Sea, we showed the general tendency of similar baseline corticosterone concentrations during both migrations, although stress-induced levels were generally much higher during spring. No difference between long- and short-distance migrants was found in either baseline or stress-induced levels, while there was substantial between-species variation, especially in baseline concentrations. The distinct patterns of corticosterone secretion during seasonal migrations even in ecologically similar species indicate that it is likely to be a species-specific trait. Thus, our study corroborates the inconsistency found in earlier studies and demonstrates how scientific understanding of the role of corticosterone during migration is still evolving. Rather low baseline corticosterone concentrations observed in this study emphasize that birds in both migratory seasons were not in a “stressed” state before capture

Size Matters: Zoo Data Analysis Shows that the White Blood Cell Ratio Differs between Large and Small Felids

The total number of white blood cells (WBCs) is related the immune system. In mammals, it is affected by the body mass, but it is unclear how the numbers of different WBC types correlate with this parameter. We analyzed the effect of body mass on WBC number and ratio in felids, where species are similar in diet (warm-blood vertebrates) and reproductive strategy (promiscuity). Based on zoo veterinary data (ZIMS database) we analyzed the effect of body mass on WBC number and neutrophils/lymphocytes ratio in 26 species of felids. The number of WBCs correlated with the body masses of animals: large cats had more WBC, which may be due to greater risks of infection associated with larger body surface, lifespan and home range size. For the first time we found obvious differences in the number of WBC types. Large cats also had more neutrophils and monocytes but fewer lymphocytes than smaller cats. The ratio of neutrophils to lymphocytes is greater in large felids. This phenomenon may be related to diet (relative prey size and kill utilization time), which suggests regular contact of large cats with bacterial and protozoal pathogens in contrast to the small cats

Assessment of physiological status of felids as an indicator of their welfare in the wild

One of the main approaches to monitoring the welfare of wild mammal populations in the wild is animal health estimation based on an analysis of their physiological parameters. To assess that for the natural felid populations, we analyzed adrenal activity level, white blood cells (WBC) counts and occurrence of seropositive reactions to different diseases. The first study was conducted in the Southwest Primorye, in natural habitats of Far Eastern leopard. Unevenly cold and snowy winters in 2010 and 2011 provided extreme natural conditions for overwintering mammals across the Russian Far East. Adrenocortical activity of leopards was significantly higher in 2011 (fecal cortisol level was 712.7 ± 92.4 ng g-1) than in 2010 (361.4 ± 80.5 ng g-1). We suggest that abundance and availability of weakened deer and carcasses could facilitate hunting for leopards and help them to avoid starvation. In the second study we used WBC counts as a health index for three felid species: Pallas cat (Daursky State Nature Biosphere Reserve, 2010), Far Eastern leopard (Southwestern Prymorie, 2011), Siberian tiger (Ussuriskii Reserve, 2010-2011). The ratio of neutrophils to lymphocytes (N:L) was used as an indicator of stress and/or disease state. Occurrence of seropositive reactions to 12 different pathogens was analyzed in all the animals after the hematological analysis. Pallas cats had the lowest N:L ratio (1.0 ± 0.1), significantly differing from leopards (42.8 ± 16.0) and tigers (24.5 ± 9.2). The N:L ratio correlated with the occurrence of seropositive reactions but not with the pathogen diversity. Pallas cats had the lowest occurrence of positive reactions to 4 pathogens: Toxoplasma gondii (12.5%), Mycoplasma sp. (12.5%), influenza A (7.1%), and feline leukemia virus (8.3%). Leopards had the highest N:L and occurrence of seropositive reactions only to 2 infections: T. gondii (16.6%) and Candida sp. (100%). On the contrary, tigers had positive responses to 6 pathogens, including canine distemper (7.7%), feline immunodeficiency virus (8.3%) and Aujeszky's disease (31%), which were not found in other cats. Values of N:L depended also on the time spent to get blood samples. In the big felid species effects of glucocorticoids on the WBC ratio (neutrophilia) were obtained in blood samples from anesthetized animals, taken more than 2 hours after capture. In Pallas cats blood samples were collected within 13 ± 2 min without anesthesia. Thus the high N:L ratio in big felids can be explained by several reasons: stress of capture, immunosuppression and a high diversity of detected infections. The present findings may have important implications for creation of effective conservation strategies of rare felid species in the wild

Comparison of tigers' fecal glucocorticoids level in two extreme habitats.

Application of different antibodies and extraction methods results in a wide range of steroid metabolite concentrations obtained during noninvasive hormones monitoring. It makes regional comparisons of steroid concentration very difficult. We compared three methods for extraction of glucocorticoids metabolites in tiger feces to examine correct stress level in Bengal and Amur tigers in India and Russia respectively. The results obtained with three different extraction methods correlate with each other positively and significantly. The highest concentration of fecal glucocorticoids metabolites (FGCM) was found after the extraction of wet feces samples with 90% methanol. The level of FGCM was significantly higher in Bengal tigers in India than in Amur tigers in Russian Far East. The reasons might be related to tigers' density or anthropogenic pressure

Predator odours as reproductive inhibitors for Norway rats

We examined the influence of predator odor on reproductive output of Norway rats (Rattus norvegicus). Naive laboratory rats responded to predator chemical cues with reduced litter sire and skewed sex ratio. We found that exposure to predator urine had its greatest effect on implantation and maintenance of implantation when predator urine was applied to the bedding of rats during the first third of gestation. Based on the physical appearance of corpora lutea and uterine implantation scars, we found that the reduction in litter sire was due to resolution of the embryos during the early part of gestation. Subsequently, we discovered that the reduction in litter sizes in rats exposed to predator urine could be attributed to suppressed progesterone levels affecting implantation of embryos. Chronically high corticoslerone levels did not suppress reproductive output. Suppression of reproduction also occurred when rats were exposed to urine of conspecifics housed under high population densities. The evolutionary adaptive response for reduced litter sire is to produce high-quality offspring in an environment where food resources are scarce. The fact that rats respond to certain chemical signals in predator urine in a similar fashion may be fortuitous, and may have more to do with the coincidence that the urine contains similar cues resulting from protein digestion in carnivores and protein catabolism in nutritionally deprived rodents, rather than specific predator-prey adaptations

Application of Felid Hair for Non-Invasive Tracking of Animal Reproductive Status and Adrenal Activity

Hair can be a useful matrix to examine the hormonal status of an animal, although it is difficult to correlate the results to a specific time point. The aim of this study was to evaluate seasonal changes in cortisol and testosterone levels in the hair of four feline species (lynx, Lynx lynx, n = 8; Amur wildcat, Prionailurus bengalensis euptilurus, n = 8; caracal, Caracal caracal, n = 6 and domestic cat, Felis catus, n = 17) with different breeding strategies. Animals of both sexes were sampled over the year, once per season (every three months), and the concentrations of hair testosterone and cortisol were measured by EIA. Both hormones showed annual dynamic changes, which coincided with the reproductive seasonality of the studied species. Sexual differences in testosterone level were found only during the mating season (spring for lynx and Amur wildcats, spring&ndash;summer for domestic cats), when testosterone levels were higher in males than in females. Cortisol levels were higher in males than in females in domestic cats and Amur wildcat, but also only during the mating season. Seasonal increases in testosterone were observed in three seasonal breeders (lynx, Amur wildcat and domestic cat) but not in caracal, which had high testosterone levels over the whole year. In lynx and Amur wildcat, it decreased sharply in the summer. Cortisol levels increased during the mating period in domestic cat males and lynx of both sexes; in caracal, an increase in cortisol was related to the transfer of animals to smaller winter cages. Measurements of steroids in hair can provide a reliable method for evaluating the reproductive status and the activity of the hypothalamus&ndash;pituitary&ndash;adrenal axis in several felid species