Non-reproductive Females Research Articles

Progress Toward Genetic Rescue of the Northern White Rhinoceros (Ceratotherium simum cottoni).

The northern white rhinoceros (NWR) is functionally extinct, with only two nonreproductive females remaining. However, because of the foresight of scientists, cryopreserved cells and reproductive tissues may aid in the recovery of this species. An ambitious program of natural and artificial gamete and in vitro embryo generation was first outlined in 2015, and many of the proposed steps have been achieved. Multiple induced pluripotent stem cell lines have been established, primordial germ cell-like cells have been generated, oocytes have been collected from the remaining females, blastocysts have been cryopreserved, and the closely related southern white rhinoceros (SWR) is being established as a surrogate. Recently, the first successful embryo transfer in SWR demonstrated that embryos can be generated by in vitro fertilization and cryopreserved. We explore progress to date in using advanced cellular technologies to save the NWR and highlight the necessary next steps to ensure a viable population for reintroduction. We roll out a holistic rescue approach for a charismatic megavertebrate that includes the most advanced cellular technologies, which can provide a blueprint for other critically endangered mammals. We also provide a detailed discussion of the remaining questions in such an upgraded conservation program.

High early lactational synchrony within baboon groups predicts increased infant mortality.

Social group composition can have fitness implications for group members by determining opportunities for affiliative and competitive interactions. Female-female competition may be particularly acute when many groupmates have young infants at the same time, with potential consequences for infant survival. Here, we used decades of data on wild baboons (Papio sp.) in Amboseli, Kenya, to examine the effects of 'early lactational synchrony' (here, the proportion of females in a group with an infant <90 days old) on female-female agonistic interactions and infant survival. Because early lactation is an energetically demanding time for mothers and a risky time for infants, we expected early lactational synchrony to produce intensified competition for food and/or male protectors, resulting in more frequent female-female agonistic interactions and high infant mortality. In support of these predictions, we found that the frequency of female-female agonistic interactions increased with increasing early lactational synchrony. Reproductive state affected this relationship: while females in all states (cycling, pregnant, and postpartum amenorrhea) initiated more agonistic interactions when early lactational synchrony was high, only females in postpartum amenorrhea (including, but not limited to, females in early lactation) received more agonistic interactions. Furthermore, while high early lactational synchrony was rare, it strongly predicted infant mortality. This association may result from both aggression among adult females and infanticidal behavior by peripubertal females. These findings provide novel evidence that social dynamics may shape reproductive phenology in a nonseasonal breeder. Specifically, both competition among reproductive females and harassment from nonreproductive females may select against synchronous reproduction.

The Response of the Gut Physiological Function and Microbiome of a Wild Freshwater Fish (Megalobrama terminalis) to Alterations in Reproductive Behavior.

The fish gut microbiome is well known for its role in degrading nutrients to improve the host's digestion and absorption efficiency. In this study, we focused on the core physiological adaptability during the various reproductive stages of the black Amur bream (Megalobrama terminalis) to explore the interaction mechanisms among the fish host gut mucosal structure, gut enzyme activity, and gut microbial metabolism in the course of the host's reproductive cycle. Our findings showed that M. terminalis exhibited locomotion metabolic type (aids in sporting) in the reproductive stage, and a change to visceral metabolic type (aids in digestion) during non-reproductive and post-reproductive stage phases. The impact of metabolic type selection and energy demand during various reproductive stages on fish nutrition strategy and digestive function was substantial. Our resulted showed that mitochondria in intestinal epithelial cells of reproductive M. terminalis appeared autophagy phenomenon, and the digestive enzyme activities in the intestines of reproductive M. terminalis were lower than those in the non-reproductive and post-reproductive individuals. Moreover, these differences in nutrition strategy have a prominent impact on the gut microbiome of reproductive M. terminalis, compared to non-reproductive and post-reproductive samples. Our findings showed that reproductive females had lower levels of alpha diversity compared to non-reproductive and post-reproductive females. Our results also showed a greater functional variety and an increase in functional genes related to carbohydrate, lipid, amino acid, cofactors, and vitamin metabolic pathways in the NRS and PRS group. It is noteworthy that an enrichment of genes encoding putative enzymes implicated in the metabolism of taurine and hypotaurine was observed in the RS samples. Our findings illustrated that the stability and resilience of the gut bacterial community could be shaped in the wild fish host-microbiome interactions during reproductive life history.

Assessing the health-fitness dynamics of endangered mountain caribou and the influence of maternal penning

The health of wildlife plays a crucial role in population demography by connecting habitat and physiology. Southern mountain caribou, a population of woodland caribou ( Rangifer tarandus caribou (Gmelin, 1978)) found in the mountains of southwest Canada, are facing significant threats. We evaluated the health of the Klinse-Za subpopulation within the central group of southern mountain caribou, which is part of an Indigenous-led conservation initiative aimed at enhancing caribou population growth through seasonal maternal penning. We collected health metrics from 46 female Klinse-Za caribou between 2014 and 2021. The health metrics included trace minerals, cortisol, biomarkers for inflammation, and pathogen prevalence. We compared these health metrics between penned and non-penned animals, reproductive and non-reproductive females, and nearby subpopulations. We provide correlative evidence linking reproductive success to trace nutrients but find no evidence for relationships with stress, exposure to pathogens, or biomarkers of inflammation. Based on the health metrics considered, Klinse-Za caribou were generally healthy relative to neighboring subpopulations and repeat capture for penning did not appear to create accumulated health issues. Penned caribou had lower fecal cortisol levels and inflammation markers compared to free-ranging animals. This work provides a baseline assessment of southern mountain caribou health and provides guidance on maternal penning activities in support of caribou recovery.

To house or oust: Honey bee (Apis mellifera) colonies can evaluate and evict drones of low quality

Across the animal kingdom, males advertise their quality to potential mates. Males of low reproductive quality, such as those that are sick, may be excluded from mating. In eusocial species, there is some evidence that reproductive females gauge the quality of their mates. However, males often spend much more time with non-reproductive females when being raised or when returning from unsuccessful mating flights. Do non-reproductive workers evaluate the quality of male reproductives? Here we address this question using male honey bees (Apis mellifera), called drones, as a model. We generated immune-challenged drones by injecting them with lipopolysaccharide and tested: 1) do workers evict immune-challenged drones from their colony, 2) do cuticular hydrocarbon (CHC) profiles, body size, or mass change when drones are immune-challenged, and 3) are these changes used by workers to exclude low quality males from the colony? We found that an immune challenge causes changes in CHC profiles of drones and reduces their body mass. Workers selectively evict small and immune-challenged drones who, themselves, do not self-evict. This work demonstrates that some eusocial males undergo an additional layer of scrutiny prior to mating mediated by the non-reproductive worker caste.Significance statementMales of some species must advertise their quality to mates but, in the case of eusocial species, must they also advertise their quality to nestmates? By manipulating honey bee male quality, we found that small and immune-challenged drones are evicted from colonies overnight. Workers may not use a drone’s cuticular hydrocarbon profile to make this assessment. This is a new example of social immunity expressed against adult males and an example of worker involvement in reproductive decisions.

Vulnerability to fluctuations in prey and predation landscape in a central place foraging marine predator

IntroductionHuman-induced environmental change is driving a global redistribution of biodiversity, resulting in shifting prey and predation landscapes. These shifting landscapes can lead to changes in behavior, health, and vital rates, with potential implications for population dynamics.MethodsIn the present study, a state-dependent life-history theory model was developed to investigate the individual- and population-level responses of Australian fur seals (Arctocephalus pusillus doriferus) to changes in prey availability and at-sea mortality risk.ResultsRates of pregnancy, pup nursing, and abortion were unaffected by prey availability in the simulated population. Likewise, on-land and at-sea durations were largely unaffected by prey availability, with more pronounced affects for nonreproductive and pregnant females than for lactating females. There was a strong influence of prey availability on the proportion of females that were concurrently pregnant and lactating, largely due to an increase in pup abandonments under low prey availability scenarios. This effect on pup abandonments also had flow on effects for pup recruitment. Increasing at-sea mortality risk resulted in greater offspring losses due to maternal death. The combined impact of prey availability and at-sea mortality risk on the number of simulated female offspring reaching sexual maturity was substantial.DiscussionConsequently, our results suggest high vulnerability of the Australian fur seal population to shifting prey and predation landscapes. These results indicate a need for continued monitoring of Australian fur seal pup production and population dynamics in the face of rapid environmental change.

The paradox of spring: Thyroid and glucocorticoid responses to cold temperatures and food availability in free living Carneddau ponies

In seasonal environments, maintaining a constant body temperature poses challenges for endotherms. Cold winters at high latitudes, with limited food availability, create opposing demands on metabolism: upregulation preserves body temperature but depletes energy reserves. Examining endocrine profiles, such as thyroid hormone triiodothyronine (T3) and glucocorticoids (GCs), proxies for changes in metabolic rate and acute stressors, offer insights into physiological trade-offs. We evaluated how environmental conditions and gestation impact on faecal hormone metabolites (fT3Ms and fGCMs) from late winter to spring in a free-living population of Carneddau ponies. Faecal T3Ms were highest in late February and March, when temperatures were lowest. Then, fT3Ms concentrations decreased throughout April and were at the lowest in May before increasing towards the end of the study. The decline in fT3M levels in April and May was associated with warmer weather but poor food availability, diet diversity and diet composition. On the other hand, fGCM levels did not display a clear temporal pattern but were associated with reproductive status, where pregnant and lactating females had higher fGCM levels as compared to adult males and non-reproductive females. The temporal profile of fT3Ms levels highlights metabolic trade-offs in a changing environment. In contrast, the ephemeral but synchronous increase in fGCM concentrations across the population suggest a shared experience of acute stressors (i.e., weather, disturbance or social). This multi-biomarker approach can evaluate the role of acute stressors versus energy budgets in the context of interventions, reproduction, seasonality and environmental change, or across multiple scales from individuals to populations.

Hydration state does not affect selected body temperature during gravidity or gravidity duration in pythons (Antaresia childreni)

The embryonic development of many ectothermic species are highly sensitive to temperature and typically have a higher thermal optima than do most other physiological processes. Thus, female ectotherms often maintain a higher and more carefully controlled body temperature when she is supporting developing embryos (early development in oviparous species, throughout development in viviparous species). Considering the positive correlation between body temperature and evaporative water loss, this response could potentially exacerbate female water imbalance in water-limited environments, suggesting that female water balance and egg development may be in conflict. Using Children's pythons (Antaresia childreni), we hypothesized that water deprivation reduces thermophily during gravidity. We split reproductive females into two thermal treatments: those provided with a continuously available thermal gradient of 25–45 °C and those kept at a constant 31 °C. We also had seven non-reproductive females that were provided a thermal gradient. Within each thermal treatment group, we alternatingly assigned females to either have or not have water throughout gravidity. We found that reproduction increased female body temperature, but this increase was not affected by water regime. Reproduction also increased plasma osmolality, and lack of water during gravidity exacerbated this effect. We also found that thermal treatment, but not water regime, significantly influenced gravidity duration, with females given a thermogradient having a shorter gravidity duration, likely as a result of having a higher average body temperature than did the females provided constant heat. Finally, we found that females provided water throughout gravidity had greater clutch masses than did females without water. Further research is needed to improve scientific understanding of the interactions among water balance, body temperature, and various physiological performances.

Body Condition of Reproductive and Non-Reproductive Broad-Snouted Caiman Females.

In this work, we calculated the body condition indices, K-Fulton and scaled mass index (SMI), of reproductive and non-reproductive Caiman latirostris adult females as an indication of stored energy. We considered 87 adult females captured from 2001 to 2018, both reproductive and non-reproductive. The body condition was calculated considering two scenarios: (a) only the weight of the female, and (b) the sum of the weight of the female and the average dry weight of her nest. We tested the difference in body condition between reproductive and non-reproductive females. We also evaluated the minimal body condition required to guarantee that females above it are reproductive by drawing a line that separated the body condition of strictly reproductive individuals from those that may or may not be reproductive. Reproductive females had better body condition than non-reproductive ones. Our SMI.S line separated almost 70% of the reproductive females. Based on our results, we can guarantee that a female whose body condition is above the line will reproduce, although not all those females below the line are non-reproductive, as a few of those under the line will nest. With this information, we have one more biological indicator to take into account when making management and conservation decisions.

Female little brown bats require both building and natural roosts in a mountainous environment with short summers

AbstractThe little brown bat (Myotis lucifugus) is an endangered species that occurs throughout most of North America. The recovery strategy for little brown bats in Canada identifies a need to understand habitat use and protect important bat habitat across the species' Canadian range; however, bat roosting habitat requirements have not been well studied in mountainous environments within the northern part of the species' range. Our objective was to understand the use of building and natural roosts by female little brown bats in the Canadian Rocky Mountains. Over two summers, we captured little brown bats in Banff, Yoho, and Kootenay National Parks, in Alberta and British Columbia, Canada, and tracked 49 females to their day roosts. Buildings were the only roost type used by radio‐tagged bats of all reproductive stages, the dominant roost type used throughout the reproductive period, and the only structures in which we located maternity colonies. Buildings also appeared to shape the distribution of foraging female and reproductive female bats such that few were captured at long distances from towns and building clusters. Compared with bats in more southern and in non‐mountainous areas, bats in our study area had delayed juvenile weaning and volancy, began hibernation early, and had low reproductive rates. We suggest that buildings are a key habitat for female little brown bats to persist at their current levels in our study area, by providing thermal conditions that promote overwinter survival; additional reproductive delays caused by torpor use in cool natural roosts would likely reduce juvenile and adult female overwinter survival below the levels required to sustain populations. Nevertheless, building colonies were unusually small, and bats had relatively low fidelity to particular building roosts, suggesting that building roosts may not consistently meet bats' needs. Some nonreproductive and pregnant females also frequently used natural roosts, particularly after colder nights; these roosts may be important in facilitating torpor and energy conservation for these bats. Because bats are long‐lived with low reproductive output and low juvenile survival, addressing the needs of both reproductive and nonreproductive individuals is important for population persistence.

Effects of age, seasonality, and reproductive status on the gut microbiome of Southern White Rhinoceros (Ceratotherium simum simum) at the North Carolina zoo

BackgroundManaged southern white rhinoceros (Ceratotherium simum simum) serve as assurance populations for wild conspecifics threatened by poaching and other anthropocentric effects, though many managed populations experience subfertility and reproductive failure. Gut microbiome and host health are inextricably linked, and reproductive outcomes in managed southern white rhinoceros may be mediated in part by their diet and gut microbial diversity. Thus, understanding microbial dynamics within managed populations may help improve conservation efforts. We characterized the taxonomic composition of the gut microbiome in the managed population of female southern white rhinoceros (n = 8) at the North Carolina Zoo and investigated the effects of seasonality (summer vs. winter) and age classes (juveniles (n = 2; 0–2 years), subadults (n = 2; 3–7 years), and adults (n = 4; >7 years)) on microbial richness and community structure. Collection of a fecal sample was attempted for each individual once per month from July-September 2020 and January-March 2021 resulting in a total of 41 samples analyzed. Microbial DNA was extracted and sequenced using the V3-V4 region of the 16S rRNA bacterial gene. Total operational taxonomic units (OTUs), alpha diversity (species richness, Shannon diversity), and beta diversity (Bray-Curtis dissimilarity, linear discriminant analysis effect size) indices were examined, and differentially enriched taxa were identified.ResultsThere were differences (p < 0.05) in alpha and beta diversity indices across individuals, age groups, and sampling months. Subadult females had higher levels of Shannon diversity (Wilcoxon, p < 0.05) compared to adult females and harbored a community cluster distinct from both juveniles and adults. Samples collected during winter months (January-March 2021) possessed higher species richness and statistically distinct communities compared to summer months (July-September 2020) (PERMANOVA, p < 0.05). Reproductively active (n = 2) and currently nonreproductive adult females (n = 2) harbored differentially enriched taxa, with the gut microbiome of nonreproductive females significantly enriched (p = 0.001) in unclassified members of Mobiluncus, a genus which possesses species associated with poor reproductive outcomes in other animal species when identified in the cervicovaginal microbiome.ConclusionTogether, our results increase the understanding of age and season related microbial variation in southern white rhinoceros at the North Carolina Zoo and have identified a potential microbial biomarker for reproductive concern within managed female southern white rhinoceros.

Climatic influences on survival and reproductive transitions of big-eared woodrats in California oak woodland

AbstractIt is known that climatic factors can influence the reproductive performance of small mammal populations. However, this information has not been available for the big-eared woodrat (Neotoma macrotis), a keystone species that inhabits the California central coast ranges south to Mexico and the oak woodlands (Quercus spp.) of the western Sierra Nevada foothills. From 2002 to 2014, we livetrapped woodrats on 1.1-ha study plots in coastal-central California and recorded their age and reproductive status. We analyzed these data by a capture-mark-recapture (CMR) framework to estimate state-specific recapture probability (p) and monthly apparent survival (S) of juvenile, non-reproductive, and reproductive adult female woodrats, and the influence of rain and temperature on S and transition probability (Ψ) of the three states. Rainfall from the previous season did not markedly affect survival rates of the states, with one exception: it decreased the survival of nonreproductive woodrats. Nearly all breeding occurred during the cool, wet winter season. Juvenile woodrats had at least a 0.55 probability of breeding by their first winter, conditional on survival. Temperature during the breeding season had a marked negative influence on transition probability. During winter, survival of nonreproductive adult females was significantly higher than for juvenile and reproductive females, indicating a cost of reproduction. Physiological effects and diminished diet quality due to further climate warming could reduce the reproductive success of female big-eared woodrats with negative consequences on population growth and persistence.

Sexual dimorphism and reproductive biology of the Asian bockadam snake (Cerberus schneiderii) in West Java

Although they are among the most abundant snakes on Earth, and are heavily exploited for their skins and meat, Asian bockadams (or “dog-faced water snakes”, Cerberus schneiderii) have attracted relatively little study across their wide geographic range. Based on dissection of 3,382 snakes brought to processing facilities in and around the city of Cirebon in West Java, Indonesia, we document facets of the biology of these mangrove-dwelling aquatic homalopsids. Females attain larger body sizes than do males, and are heavier-bodied (due in part to greater fat reserves) but have shorter tails relative to snout-vent length. Males showed testicular enlargement late in the year (August-November) but both reproductive and non-reproductive females were found year-round. Litters were large (3 to 45 offspring), especially in larger females. The commercial harvest falls mainly on adult snakes of both sexes, with seasonal variation in sex ratios. Life-history traits such as early maturation and frequent production of large litters render this species resilient to commercial harvesting. Future research should explore reasons for strong variation among facilities in the sex ratios of snakes, potentially identifying ways to focus the harvest on the sex (males) whose numbers are less critical for population viability.

Socially Induced Infertility in Naked and Damaraland Mole-Rats: A Tale of Two Mechanisms of Social Suppression.

The naked mole-rat (Heterocephalus glaber) and the Damaraland mole-rat (Fukomys damarensis) possess extreme reproductive skew with a single reproductive female responsible for reproduction. In this review, we synthesize advances made into African mole-rat reproductive patterns and physiology within the context of the social control of reproduction. Non-reproductive female colony members have low concentrations of luteinising hormone (LH) and a reduced response of the pituitary to a challenge with gonadotropin releasing hormone (GnRH). If the reproductive female is removed from the colony, an increase in the basal plasma LH and increased pituitary response to a GnRH challenge arises in the non-reproductive females, suggesting the reproductive female controls reproduction. Non-reproductive male Damaraland mole-rats have basal LH concentrations and elevated LH concentrations in response to a GnRH challenge comparable to the breeding male, but in non-breeding male naked mole-rats, the basal LH concentrations are low and there is a muted response to a GnRH challenge. This renders these two species ideal models to investigate physiological, behavioural and neuroendocrine mechanisms regulating the hypothalamic-pituitary-gonadal axis. The recently discovered neuropeptides kisspeptin and RFamide-related peptide-3 are likely candidates to play an important role in the regulation of reproductive functions in the two mole-rat species.

The impact of size truncation on reproductive success in the southern king crab (Lithodes santolla)

Sex-biased fishing mortality caused by male-only fishing may result in sperm limitation and recruitment overfishing. These effects can be observed by studying the size at functional reproduction (SFR) of lithodid females. We studied changes in the ratio of males to females, size truncation, and changes in SFR in the southern king crab (SKC) in two areas experiencing different fishing pressures in southern Chile. SFR was estimated with the Richards Function, a generalized 4-parameter logistic model. The shrinking of SFR of females may occur due to the proportional shrinking of reproductive and non-reproductive females and/or because the shape of the ogive changes, setting the inflection point back to smaller sizes. In the region with low fishing pressure the functional reproductive ogive was symmetric (γ = 1, and the asymptote was ∼1, indicating a balance in male availability. In the region with high fishing pressure γ was 82 % lower and the asymptote was 23 % lower, an indicator of sperm limitation. The symmetric shape of the logistic curve, which is widely assumed when fitting maturity ogives, is not the most appropriate assumption in SKC and possibly in other males-only crab fisheries. More general shapes of the ogive should be estimated and studied.

Microhabitat, diet, and reproductive activity of a population of the Andean shrew Cryptotis tamensis (Eulipotyphla: Soricidae)

ABSTRACT The Tamá small-eared shrew is found in the Andean cloud forests of the Cordillera Oriental of Colombia and the Tamá paramo in western Venezuela. Few aspects of its biology are known, and all information comes from its original description. In a patch of oak cloud forest, we found a relatively abundant population of the species and studied its abundance, microhabitat preference, diet composition and reproductive features, and their relationship with the rainfall seasonality of the study area. The fieldwork was carried on for two years at altitudinal intervals from 2402 to 2627 m.a.s.l. We caught 44 shrews in microhabitats with dense vegetation cover, abundant litter and fallen trees; their abundance changed significantly through time, varying along with the precipitation of the month before the capture. We found seven groups of arthropods in their diet, the composition of which did not differ significantly between sexes, reproductive stages or seasons. These shrews have a specialised diet, with ants as the most important item. Reproductive males are distinguished externally by the presence of hypertrophic subcutaneous lateral glands. We found adult reproductive males and non-reproductive males throughout the duration of the study, and their abundance did not vary significantly with precipitation. In contrast, we did not capture females in the driest months of the years, and although adult non-reproductive females were also found, we found a significant relationship between the abundance of reproductive females and precipitation. Consequently, adult reproductive males would be a permanent reproductive resource for the females, which appear to adjust their reproductive activity during the rainy seasons.

Flexible energy-saving strategies in female temperate-zone bats

Torpor is characterized by an extreme reduction in metabolism and a common energy-saving strategy of heterothermic animals. Torpor is often associated with cold temperatures, but in the last decades, more diverse and flexible forms of torpor have been described. For example, tropical bat species maintain a low metabolism and heart rate at high ambient and body temperatures. We investigated whether bats (Nyctalus noctula) from the cooler temperate European regions also show this form of torpor with metabolic inhibition at high body temperatures, and whether this would be as pronounced in reproductive as in non-reproductive bats. We simultaneously measured metabolic rate, heart rate, and skin temperature in non-reproductive and pregnant females at a range of ambient temperatures. We found that they can decouple metabolic rate and heart rate from body temperature: they maintained an extremely low metabolism and heart rate when exposed to ambient temperatures changing from 0 to 32.5 °C, irrespective of reproductive status. When we simulated natural temperature conditions, all non-reproductive bats used torpor throughout the experiment. Pregnant bats used variable strategies from torpor, to maintaining normothermy, or a combination of both. Even a short torpor bout during the day saved up to 33% of the bats' total energy expenditure. Especially at higher temperatures, heart rate was a much better predictor of metabolic rate than skin temperature. We suggest that the capability to flexibly save energy across a range of ambient temperatures within and between reproductive states may be an important ability of these bats and possibly other temperate-zone heterotherms.

The thermal neutral zone is shifted during lactation in striped hamsters

The thermoneutral zone (TNZ), one of the most well-recognized concepts of thermal physiology of homeothermic organisms, is observed to differ between animal species, and may be associated with energy expenditure. However, the characteristics of the TNZ of lactating females, the stage of life history with typically the highest energy demands, remain unclear. In this study, we examined body mass, metabolic rate, TNZ and body composition, and milk energy output, in striped hamsters (Cricetulus barabensis, mean body mass: 29.1 ± 4.4g ranging from 20.0 to 36.6g) at peak lactation, and in hamsters raising small, medium, and large litter sizes throughout lactation.There was a significant downward shift in the lower critical temperature (LCT) of the TNZ in lactating hamsters (TNZ = 22.5–35 °C), resulting in a wider TNZ compared to non-reproductive females (TNZ = 27.5–32.5 °C). At peak lactation, hamsters raising large litter sizes had a considerably lower LCT and a wider TNZ compared to hamsters raising medium and small sized litters, whose upper critical temperature of the TNZ remain fixed. Compared to virgin hamsters, hamsters at peak lactation consumed 2.5 times more food, and had significantly higher energy expenditure corresponding to a significantly higher resting metabolic rate and milk output to meet the requirements of their offspring, which increased with litter size. The organs with the highest oxygen consumption rates, such as the liver, kidneys, and digestive tracts, were considerably heavier in lactating hamsters, particular in those raising large litter sizes, compared to virgin hamsters. The data show that the increased energy expenditure during lactation induces a substantial downward shift of the LCT, consequently resulting in a wider TNZ. The morphological plasticity of organs with high energy requirements is likely involved in this TNZ shift.

Sex-Specific Movement Responses of Reeves's Pheasant to Human Disturbance: Importance of Body Characteristics and Reproductive Behavior.

Simple SummaryHuman disturbance has a strong impact on the movement of wild animals. The Reeves’s Pheasant is listed as an endangered species by the International Union for Conservation of Nature (IUCN) and a nationally protected species in China. This study evaluated how the movement patterns of this species responded to human disturbance. We observed large differences in movement characteristics between sexes during the breeding season of Reeves’s Pheasants, and found that reproduction had a significant effect on the movement of females. Males shifted their movement peaks to earlier times in the day to avoid the presence peaks of humans. The greater the distance to human-modified habitat, the higher the movement intensity of males, and the lower the movement intensity of females. This study suggested that the potential impacts of different forms of human disturbance on wildlife should be considered in future conservation planning.Human disturbance has a strong impact on the movement of wild animals. However, it remains unclear how the movement patterns of the Reeves’s Pheasant (Syrmaticus reevesii) respond to human disturbance in human-dominated landscapes. We tracked the movement of 40 adult individual Reeves’s Pheasants during the breeding season, and used the dynamic Brownian bridge motion model and kernel density estimation to analyze the diurnal movement patterns of Reeves’s Pheasants and their response to human presence. We analyzed the paths of Reeves’s Pheasants based on a partial least squares path model, considering habitat conditions, body characteristics, and reproductive behaviors. We found that males had two clear diurnal movement peaks, whereas reproductive and non-reproductive females did not show such movement peaks. Males shifted their movement peaks to earlier times in the day to avoid the presence peaks of humans. The correlation between human-modified habitat and the movement intensity of Reeves’s Pheasant differed between sexes. For males, the distance to forest paths had a positive correlation with their movement intensity through affecting body conditions. For females, the distance to forest paths and farmland had a negative correlation with their movement intensity through affecting habitat conditions and reproductive behaviors. Our study provides a scientific basis for the protection of the Reeves’s Pheasant and other related terrestrial forest-dwelling birds.

Reproductive status affects isotopic niches of Miniopterus natalensis in northeastern South Africa

Abstract The Natal long-fingered bat, Miniopterus natalensis, is an insectivorous, regional migrating species that exhibits sex-specific migration patterns. We explored the variability of isotopic niches using δ13C and δ15N ratios in fur from female and male bats in different reproductive states: pregnant, reproductive (but not pregnant at the time of this study), and nonreproductive females; nonscrotal and scrotal males using Bayesian standard ellipse areas and generalized linear models. Reproductive status was an informative predictor for the observed variation of both δ13C and δ15N ratios. Pregnant females displayed the highest mean δ13C and δ15N ratios and were distinct from other reproductive states. Reproductive females exhibited significantly higher δ15N ratios than nonreproductive females or nonscrotal and scrotal males, which may reflect state-dependent foraging and/or higher metabolic stress. Scrotal males displayed the lowest mean δ13C and δ15N ratios. Nonscrotal males exhibited the broadest isotopic niche, whereas reproductive females had the narrowest isotopic niche. Differences in isotopic niche sizes between the different reproductive groups may relate to variable individual feeding behavior and/or geographically different foraging areas/migratory stopover sites at individual and intraspecific levels in M. natalensis. This suggests that group-living, cave-dwelling bats may employ individual foraging specialization to facilitate coexistence in the broader geographic landscape.