Juvenile survival is a key life-history influence on population dynamics and adaptive evolution.We analyzed the effects of individual chara-cteristics,early environment,and maternal investment on juvenile survival in ...Juvenile survival is a key life-history influence on population dynamics and adaptive evolution.We analyzed the effects of individual chara-cteristics,early environment,and maternal investment on juvenile survival in a large solitary hibernating rodent-yellow ground squirrel Spermophilus fulvus using Cox mixed-effects models.Only 48%of weaned pups survived to dispersal and 17%survived to hibernation.Early life expectancy was primarily determined by individual characteristics and,to a lesser extent,by the early environment.The strongest and pos-itive predictor of juvenile survival was body mass which crucially affected mortality immediately after weaning.Males suffered higher mortality than females after the onset of dispersal;however,the overall difference between sexes was partly masked by high rates of mortality in the first days after emergence in both sexes.Later emerged juveniles had lower life expectancy than the earliest pups.The overall effect of local juvenile density was positive.Prolonged lactation did not enhance juvenile survival:Pups nursed longer survived shorter than the young nursed for a shorter period.Our findings support the hypothesis that females of S.fulvus cannot effectively regulate maternal expenditures to mitigate the effects of unfavorable conditions on their offspring.The strategy to deal with seasonal time constraints on life history in female S.fulvus suggests an early termination of maternal care at the cost of juvenile quality and survival.This female reproductive strategy corresponds to a"fast-solitary"life of folivorous desert-dwelling S.fulvus and other solitary ground squirrels with prolonged hibernation.展开更多
The Himalayan marmot Marmota himalayana is widely distributed across the Qinghai-Tibetan Plateau and lives in social groups,yet the mating system of this highly social marmot species is unknown.In this study,the genet...The Himalayan marmot Marmota himalayana is widely distributed across the Qinghai-Tibetan Plateau and lives in social groups,yet the mating system of this highly social marmot species is unknown.In this study,the genetic mating system of Himalayan marmots was inves-tigated using microsatellite markers to determine which mating strategies individuals employ.Results revealed that both monogamous and polygamous mating relationships occur in our study population,indicating that the genetic mating system of this marmot species is promiscuity.This study presents the first genetic evidence on the mating system for Himalayan marmots,yet indicates that further studies employing both a genetic and behavioral framework are needed to better understand the social structure and reproductive biology of this marmotspecies.展开更多
We validated a radioimmunoassay-based method quantifying fecal glucocorticoid metabolites （FGMs） from captive male and female Richardson＇s ground squirrels Urocitellus richardsonii. Blood samples were drawn to expl...We validated a radioimmunoassay-based method quantifying fecal glucocorticoid metabolites （FGMs） from captive male and female Richardson＇s ground squirrels Urocitellus richardsonii. Blood samples were drawn to explore the correlation between plasma cortisol and FGM concentrations. We also injected groups of squirrels with normal saline （CTL; control）, adre- nocorticotropic hormone （ACTH; stimulating adrenal activity）, or dexamethasone （DEX; suppressing adrenal activity）. Potential correlations between stress and behaviour were explored through quantification of fecal pellet production and the intervention necessary to elicit defecation, as well as the behaviour of subjects in the context of handling. Changes in plasma cortisol concen- tration between capture （baseline）, and following handling （stress-induced） were also quantified for free-living squirrels. While glucocorticoid concentrations recovered from feces during our captive-animal study were not well correlated with plasma eortisol concentrations, and uncorrelated with defecation or behaviour, FGM concentrations did reflect the activation of the hypothalamic- pituitary-adrenal （HPA） axis. FGM concentrations increased significantly during initial captivity, but declined to baseline level as individuals acclimated to the novel environment. Injection of subjects with ACTH increased FGMs above baseline, confirming activation of the HPA axis. Plasma cortisol concentrations increased significantly with induced stress, indicating that capture and handling activated the glucocorticoid stress response even among previously handled, free-living subjects. Our findings validate a non-invasive tool that will afford new insight into the physiological processes underlying social, reproductive and antipredator behaviour of Richardson＇s ground squirrels [Current Zoology 60 （5）： 591-601, 2014 ].展开更多
Hole-nesting tits belonging to the family Paridae produce a hissing display that resembles the exhalatory hiss of a snake.When a predatory animal enters the nest hole of a tit,tits often hiss vigorously,while lunging ...Hole-nesting tits belonging to the family Paridae produce a hissing display that resembles the exhalatory hiss of a snake.When a predatory animal enters the nest hole of a tit,tits often hiss vigorously,while lunging their head forward and shaking their wings and tail,until the intruder retreats.We assessed the acoustic similarity between such hiss calls from 6 species of tits,snake hisses,and tit syllables used in alarm vocalizations,as well as white noise as a control.Tit hiss calls showed a high degree of similarity with snake hisses from 3 different snake families.Tit hisses had lower similarity to syllable alarm calls,suggesting convergence of tit hisses in their spectral structure.Hiss calls would only be effective in protecting nest boxes if nest predators responded to these calls.In order to test this hypothesis,we trained individual Swinhoe’s striped squirrels,Tamiops swinhoei hainanus,a common predator of egg and nestling tits,to feed at feeders in proximity to nest boxes.We compared the aversive response of squirrels to tit’s hiss calls and white noise,presented in random order.Squirrels showed a higher degree of avoidance of feeders when hiss calls were played back than when white noise was presented.In conclusion,our study suggests that hole-nesting birds have evolved convergent snake-like hiss calls,and that predators avoid to prey on the contents of nest boxes from which snake-like hisses emerge.展开更多
In polymorphic mammalian species that display multiple color forms, those with dark, or melanic pelage would be prone to overheating, especially if they live in warm climates, because their fur absorbs solar energy at...In polymorphic mammalian species that display multiple color forms, those with dark, or melanic pelage would be prone to overheating, especially if they live in warm climates, because their fur absorbs solar energy at a higher rate. However, experimental studies indicate that certain physical properties of fur of dark individuals appear to prevent, or minimize heat stress, although it is not clear what properties do so. Here, we tested the possibility that black-furred individuals simply have shorter or thinner hair fibers, which would create a lighter （in terms of weight） coat or one that allows greater air flow for evaporative coo- ling. We examined museum specimens of eastern fox squirrels Sciurus niger, a species native to the United States and one that displays brown, grey or all-black pelage color, and used image analysis procedures to quantify hairs from the dorsal surface and tail. From examination of 43 specimens （19 brown, 9 black and 15 grey）, and 1,720 hairs, we found no significant difference in hair lengths across color morphs, but significant differences in hair fiber widths. Black squirrels had thinner body hairs than other forms （7% thinner）, but thicker tail hairs （9% thicker） than the others. Given that the dorsal surface would be directly exposed to solar radiation, we interpret this to be an adaptation to prevent heat stress during the day. The thicker tail hairs may be an adapta- tion for nighttime thermoregulation, since squirrels sleep with their tails wrapped around their bodies. These results add to a growing literature body of the functional significance of mammalian pelage [Current Zoology 57 （6）： 731-736, 2011].展开更多
Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam.The transects comprised two strata:traps were pla...Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam.The transects comprised two strata:traps were placed on the ground and in the canopy 2–12 m above the ground.At the main transect,which was 1500 m long and located in undisturbed forest,a total of 438 rodents(173 squirrels and 265 murids)of 12 different species(one Scuridae sp.;11 Muridae spp.)were marked between January 2005 and January 2006.At this study site and at another undisturbed tropical forest site in the same area,two species dominated:the rat Maxomys surifer(Miller,1900)and the squirrel Callosciurus flavimanus(Geoffroy,1831).During the study period we observed no significant difference between the average abundances of the two species(4.67±0.86 and 3.1±0.85 individuals per 100 trap nights,respectively)or between the average proportions of resident squirrels and rats(60.0±24.1 and 62.5±11.5,respectively).The number of squirrels that were permanent residents(i.e.dwelling in the same habitat for 1 year)was eightfold the number of rats that were permanent residents.In addition,there was some synchrony in the daily capture dynamics of squirrels and of rats.We observed no significant difference in the total abundance of small mammals between the arboreal and ground strata.At two disturbed tropical forest sites in the same area,however,no such balance between squirrels and rats was observed,and the density of C.flavimanus was very low.We suggest that the relationship between these two dominant species can act as an indicator of the integrity of tropical forest ecosystems in south Vietnam.展开更多
Over the past decade,extensive poisoning campaigns have been conducted in southern Saskatchewan to control Richardson’s ground squirrel Spermophilus richardsonii(Sabine,1822)populations.Such campaigns might impact on...Over the past decade,extensive poisoning campaigns have been conducted in southern Saskatchewan to control Richardson’s ground squirrel Spermophilus richardsonii(Sabine,1822)populations.Such campaigns might impact on predator abundance by decreasing prey levels,and also through secondary poisoning.Using spotlighting,we investigated the relative abundance of American badgers Taxidea taxus(Schreber,1777)and red fox Vulpes vulpes(Linnaeus,1758)in 2 study areas with road access and crops,but with different levels of poisoning.In the study area with relatively low poisoning(19.6%of the area traversed by roads),there were 2.2 times more American badgers per km of road and 6.4 times more red foxes per km than in the study area with high poisoning(89.7%of the area).It is recommended that an Integrated Pest Management program be developed to conserve natural predators across landscapes.展开更多
基金supported by the Russian Science Foundation,project number 22-24-00610,https://rscf.ru/project/22-24-00610/.
文摘Juvenile survival is a key life-history influence on population dynamics and adaptive evolution.We analyzed the effects of individual chara-cteristics,early environment,and maternal investment on juvenile survival in a large solitary hibernating rodent-yellow ground squirrel Spermophilus fulvus using Cox mixed-effects models.Only 48%of weaned pups survived to dispersal and 17%survived to hibernation.Early life expectancy was primarily determined by individual characteristics and,to a lesser extent,by the early environment.The strongest and pos-itive predictor of juvenile survival was body mass which crucially affected mortality immediately after weaning.Males suffered higher mortality than females after the onset of dispersal;however,the overall difference between sexes was partly masked by high rates of mortality in the first days after emergence in both sexes.Later emerged juveniles had lower life expectancy than the earliest pups.The overall effect of local juvenile density was positive.Prolonged lactation did not enhance juvenile survival:Pups nursed longer survived shorter than the young nursed for a shorter period.Our findings support the hypothesis that females of S.fulvus cannot effectively regulate maternal expenditures to mitigate the effects of unfavorable conditions on their offspring.The strategy to deal with seasonal time constraints on life history in female S.fulvus suggests an early termination of maternal care at the cost of juvenile quality and survival.This female reproductive strategy corresponds to a"fast-solitary"life of folivorous desert-dwelling S.fulvus and other solitary ground squirrels with prolonged hibernation.
基金supported by the National Natural Science Foundation of China(32171487)State Forestry and Grassland Administration Bureau of ChinaPostdoctoral Research Grants at the Central South University of Forestry and Technology(45220003).
文摘The Himalayan marmot Marmota himalayana is widely distributed across the Qinghai-Tibetan Plateau and lives in social groups,yet the mating system of this highly social marmot species is unknown.In this study,the genetic mating system of Himalayan marmots was inves-tigated using microsatellite markers to determine which mating strategies individuals employ.Results revealed that both monogamous and polygamous mating relationships occur in our study population,indicating that the genetic mating system of this marmot species is promiscuity.This study presents the first genetic evidence on the mating system for Himalayan marmots,yet indicates that further studies employing both a genetic and behavioral framework are needed to better understand the social structure and reproductive biology of this marmotspecies.
文摘We validated a radioimmunoassay-based method quantifying fecal glucocorticoid metabolites （FGMs） from captive male and female Richardson＇s ground squirrels Urocitellus richardsonii. Blood samples were drawn to explore the correlation between plasma cortisol and FGM concentrations. We also injected groups of squirrels with normal saline （CTL; control）, adre- nocorticotropic hormone （ACTH; stimulating adrenal activity）, or dexamethasone （DEX; suppressing adrenal activity）. Potential correlations between stress and behaviour were explored through quantification of fecal pellet production and the intervention necessary to elicit defecation, as well as the behaviour of subjects in the context of handling. Changes in plasma cortisol concen- tration between capture （baseline）, and following handling （stress-induced） were also quantified for free-living squirrels. While glucocorticoid concentrations recovered from feces during our captive-animal study were not well correlated with plasma eortisol concentrations, and uncorrelated with defecation or behaviour, FGM concentrations did reflect the activation of the hypothalamic- pituitary-adrenal （HPA） axis. FGM concentrations increased significantly during initial captivity, but declined to baseline level as individuals acclimated to the novel environment. Injection of subjects with ACTH increased FGMs above baseline, confirming activation of the HPA axis. Plasma cortisol concentrations increased significantly with induced stress, indicating that capture and handling activated the glucocorticoid stress response even among previously handled, free-living subjects. Our findings validate a non-invasive tool that will afford new insight into the physiological processes underlying social, reproductive and antipredator behaviour of Richardson＇s ground squirrels [Current Zoology 60 （5）： 591-601, 2014 ].
基金supported by the National Natural Science Foundation of China(Nos.31472013 and 31772453 to W.L.).
文摘Hole-nesting tits belonging to the family Paridae produce a hissing display that resembles the exhalatory hiss of a snake.When a predatory animal enters the nest hole of a tit,tits often hiss vigorously,while lunging their head forward and shaking their wings and tail,until the intruder retreats.We assessed the acoustic similarity between such hiss calls from 6 species of tits,snake hisses,and tit syllables used in alarm vocalizations,as well as white noise as a control.Tit hiss calls showed a high degree of similarity with snake hisses from 3 different snake families.Tit hisses had lower similarity to syllable alarm calls,suggesting convergence of tit hisses in their spectral structure.Hiss calls would only be effective in protecting nest boxes if nest predators responded to these calls.In order to test this hypothesis,we trained individual Swinhoe’s striped squirrels,Tamiops swinhoei hainanus,a common predator of egg and nestling tits,to feed at feeders in proximity to nest boxes.We compared the aversive response of squirrels to tit’s hiss calls and white noise,presented in random order.Squirrels showed a higher degree of avoidance of feeders when hiss calls were played back than when white noise was presented.In conclusion,our study suggests that hole-nesting birds have evolved convergent snake-like hiss calls,and that predators avoid to prey on the contents of nest boxes from which snake-like hisses emerge.
文摘In polymorphic mammalian species that display multiple color forms, those with dark, or melanic pelage would be prone to overheating, especially if they live in warm climates, because their fur absorbs solar energy at a higher rate. However, experimental studies indicate that certain physical properties of fur of dark individuals appear to prevent, or minimize heat stress, although it is not clear what properties do so. Here, we tested the possibility that black-furred individuals simply have shorter or thinner hair fibers, which would create a lighter （in terms of weight） coat or one that allows greater air flow for evaporative coo- ling. We examined museum specimens of eastern fox squirrels Sciurus niger, a species native to the United States and one that displays brown, grey or all-black pelage color, and used image analysis procedures to quantify hairs from the dorsal surface and tail. From examination of 43 specimens （19 brown, 9 black and 15 grey）, and 1,720 hairs, we found no significant difference in hair lengths across color morphs, but significant differences in hair fiber widths. Black squirrels had thinner body hairs than other forms （7% thinner）, but thicker tail hairs （9% thicker） than the others. Given that the dorsal surface would be directly exposed to solar radiation, we interpret this to be an adaptation to prevent heat stress during the day. The thicker tail hairs may be an adapta- tion for nighttime thermoregulation, since squirrels sleep with their tails wrapped around their bodies. These results add to a growing literature body of the functional significance of mammalian pelage [Current Zoology 57 （6）： 731-736, 2011].
文摘Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam.The transects comprised two strata:traps were placed on the ground and in the canopy 2–12 m above the ground.At the main transect,which was 1500 m long and located in undisturbed forest,a total of 438 rodents(173 squirrels and 265 murids)of 12 different species(one Scuridae sp.;11 Muridae spp.)were marked between January 2005 and January 2006.At this study site and at another undisturbed tropical forest site in the same area,two species dominated:the rat Maxomys surifer(Miller,1900)and the squirrel Callosciurus flavimanus(Geoffroy,1831).During the study period we observed no significant difference between the average abundances of the two species(4.67±0.86 and 3.1±0.85 individuals per 100 trap nights,respectively)or between the average proportions of resident squirrels and rats(60.0±24.1 and 62.5±11.5,respectively).The number of squirrels that were permanent residents(i.e.dwelling in the same habitat for 1 year)was eightfold the number of rats that were permanent residents.In addition,there was some synchrony in the daily capture dynamics of squirrels and of rats.We observed no significant difference in the total abundance of small mammals between the arboreal and ground strata.At two disturbed tropical forest sites in the same area,however,no such balance between squirrels and rats was observed,and the density of C.flavimanus was very low.We suggest that the relationship between these two dominant species can act as an indicator of the integrity of tropical forest ecosystems in south Vietnam.
文摘Over the past decade,extensive poisoning campaigns have been conducted in southern Saskatchewan to control Richardson’s ground squirrel Spermophilus richardsonii(Sabine,1822)populations.Such campaigns might impact on predator abundance by decreasing prey levels,and also through secondary poisoning.Using spotlighting,we investigated the relative abundance of American badgers Taxidea taxus(Schreber,1777)and red fox Vulpes vulpes(Linnaeus,1758)in 2 study areas with road access and crops,but with different levels of poisoning.In the study area with relatively low poisoning(19.6%of the area traversed by roads),there were 2.2 times more American badgers per km of road and 6.4 times more red foxes per km than in the study area with high poisoning(89.7%of the area).It is recommended that an Integrated Pest Management program be developed to conserve natural predators across landscapes.
