Mammal Study
Volume 44, Issue 2, 2019
Volumes & issues:
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REVIEW
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Ecological and Biological Characteristics for the Risso's Dolphins (Grampus griseus) Off Taiwan, with Conservation Evaluations on Potential Anthropogenic Threats
View Description Hide DescriptionAbstract.Risso's dolphin (Grampus griseus) is one of the cetacean species commonly encountered off the eastern coast of Taiwan. The species appears to occur in Taiwanese waters year-round. Many biological and ecological characteristics, including group size, habitat preference, and ages at weaning and sexual maturity, are by-and-large in accord with earlier reports for populations in other geographic regions. Morphological assessments, dietary analyses, and genetic data altogether suggest the dolphins found in Taiwanese and Japanese waters are from the same population, which exhibits high genetic diversity and a sign of recent demographic expansion. The dolphin species is endorsed a “Rare and Valuable Species (Class II)” status and is protected by the Wildlife Conservation Act in Taiwan. However, it is still vulnerable to human activities, in terms of whale-watching tourism and coastal gill-net fisheries, with a growing concern on the level of heavy metal residues found in dolphin tissues. Current knowledge for the species is mostly derived from relatively limited information. Assessments on key biological and ecological features, e.g., population size, residency, social structure, and group composition, shall be prioritised for conservation initiatives.
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ORIGINAL PAPERS
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Population Genetic Study of the Lesser Japanese Mole Mogera imaizumii using Novel Microsatellite Markers with Special Reference to Sex-Biased Dispersal
View Description Hide DescriptionAbstract.Sex-biased dispersal (SBD) is usually accounted for by the consequences of resource competition, inbreeding avoidance, and breeding competition. Although SBD has been reported in many mammalian species, little is known about it in subterranean species, like moles, whose dispersal from a natal place cannot be easily studied using conventional methods such as direct observations and radio-telemetry. Here, we used a genetic approach to study the population structure of the lesser Japanese mole Mogera imaizumii and tested whether SBD occurs in these solitary moles. We collected samples from three local populations in northern Japan and developed 12 novel microsatellite markers for genetic analyses. Population-based analyses showed a significant genetic differentiation among the populations. In individual-based analyses, we tested the degree of SBD using two different approaches: genetic relatedness between individuals and corrected assignment index (AIc). There was no significant difference in mean genetic relatedness and mean AIc between male and female groups in all three populations, although the proportion of individuals with positive AIc was higher in females than males in all three populations. The new microsatellite markers will help understanding of population genetic structure and behavior of moles in the further study.
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Validation of Body Condition Indicators for Monitoring Changes in Populations of Sika Deer (Cervus nippon) at a Landscape Scale
View Description Hide DescriptionAbstract.The estimated number of sika deer within the Tanzawa Mountains has decreased since the Kanagawa Prefecture sika deer management plan commenced. Meanwhile, unit-specific culling has resulted in various trends in deer density across small monitoring units. Deer abundance is usually surveyed within small monitoring units; therefore, the evaluation of deer abundance changes across the entire management area comprising individual units is difficult. We examined the relationship between deer body condition indicators and densities estimated at both individual unit and entire management scales in the Tanzawa Mountains during 2004–2015. Winter fawn body mass in the study area increased at least until 2011, irrespective of the increase/decrease in deer density in each unit. Observed variations in body mass were related to the estimated number of deer within the entire management area. Winter fawn hind foot length was not related to any density estimates. Inconsistencies between deer density changes in each unit and body mass might derive from the deer movement between units and mitigation of density-dependent food limitations caused by a reduction in the number of deer within the entire management area. We suggest that winter fawn body mass can provide additional evidence of deer abundance changes within management areas.
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Nomadic Movement of Mongolian Gazelles Identified through the Net Squared Displacement Approach
View Description Hide DescriptionAbstract.The Mongolian gazelles (Procapra gutturosa) that inhabit Mongolia's steppe and semi-desert travel several hundred kilometers each year. Their movement pattern has been considered nomadic, but the details of their movement patterns remain unclear. The aim of this study is to gain an overall perspective of the movement of Mongolian gazelles, which experience diverse environmental conditions with large interannual variations across their continuous distribution range. Based on net squared displacement (NSD) modeling approach, the mixed migration type was the most observed type in the statistical assignment among five movement types, and some movements were assigned into the migration or sedentary. However, NSD seasonal change was irregular in the most annual movements of gazelles, suggesting the nomadic movements of individuals. Most gazelles tracked for more than a year changed their movement types annually, and the movement period differed among individuals. These results also support nomadic movement of the species, although some difficulties of modeling nomadism by the NSD approach were revealed.
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Seasonal Changes in the Home Range of the Antelope Jackrabbit (Lepus alleni)
View Description Hide DescriptionAbstract.In the face of climate change, more research is needed to understand how animals adjust to dynamic ecosystems. Seasonal environments offer a unique opportunity to observe how animals use the landscape in a fluctuating system. The antelope jackrabbit (Lepus alleni) is an understudied lagomorph found in the Sonoran Desert of Arizona, USA and Mexico. Basic ecological information on this species is lacking beyond historical responses to rangeland conditions. Using radio telemetry, we collected data on home range size and seasonal ranges of antelope jackrabbits on the Buenos Aires National Wildlife Refuge in southcentral Arizona. Male and female antelope jackrabbit mean home range size differed slightly, though not significantly. Within a seasonal landscape of semidesert and Sonoran savanna grasslands, antelope jackrabbits seasonal range size did not change but the home range usage percentage differed across seasons and degree of interseason similarity was low. Antelope jackrabbit home ranges are comparable to range sizes reported for the widespread black-tailed jackrabbit (Lepus californicus) as well as the closely related Tehuantepec jackrabbit (Lepus flavigularis). This study is the first to document antelope jackrabbit home range, and our results permit a better understanding of how these hares use the landscape in a complex arid environment.
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SHORT COMMUNICATIONS
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Seed Feeding Behavior of Diplothrix legata (Muridae: Rodentia): Effects on Germination of Five Plants in Okinawajima Island, Japan
View Description Hide DescriptionAbstract.This study examined how seed feeding by the Ryukyu long-furred rat Diplothrix legata affects germination of five plants (Cerasus campanulata, Actinidia rufa, Ficus erecta, Oreocnide pedunculata, and Melastoma candidum) in Okinawajima Island, Japan. The germination rates of seeds from fresh fruit and fecal pellets of two captive rats, as well as the feeding behaviors, were observed. Most of C. campanulata seeds, which were the largest among the five plant species, were crushed by rats. Seeds of the other four plants were swallowed whole; however, the excretion rates were low (< 20%). The germination rates of A. rufa, F. erecta, and M. candidum from fecal pellets were significantly lower than that of seeds from fresh fruits. The rats showed a higher excretion rate for the seeds of O. pedunculata, and the excreted seeds showed a similar germination rate to that of seeds from fresh fruits, which might be attributed to the small-sized seeds with hard coats. Some fruits of A. rufa and F. erecta were dropped before they were completely consumed. Thus, undigested seeds and dropped seeds might be dispersed by D. legata, although this species should be regarded mainly as a seed predator.
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Reproductive Ability of Elderly Male Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Captivity
View Description Hide DescriptionAbstract.The present study, the first to examine breeding ability in elderly cetaceans, addressed the reproductive capacity of four captive male Indo-Pacific bottlenose dolphins that are among the oldest in the world (47–50 years in 2017). The dolphins' reproductive ability was assessed by monthly monitoring of serum testosterone (T) levels over nine years (2009–2017), and examination of semen characteristics. Serum T concentrations from blood samples were measured by fluorescence immunoassay. The dolphins showed regular peaks in their serum T levels every year or once every few years. The mean monthly T level showed a significant seasonal change, beginning to elevate in January, peaking from March to May, and then declining until September. Semen production was confirmed in three of the four individuals, and semen quality was confirmed for those dolphins through collections one or two times a month for a year. The sperm concentration in samples from those individuals was comparatively high. These data indicated that the dolphins had the capacity to breed every year. Indo-Pacific bottlenose dolphins are capable of surviving to older ages in captivity than they typically reach in the wild, and it is likely that even elderly individuals retain their breeding ability.
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First Record of Petinomys setosus (Rodentia: Sciuridae: Pteromyini) from Lao PDR
View Description Hide DescriptionAbstract.The first known occurrence of Petinomys setosus in Lao People's Democratic Republic (PDR) was recorded from a single specimen collected at Na Mouang village in Vientiane province, which is approximately 240 km from its nearest known distribution in northwestern Thailand. We describe the morphological and cranial features of this specimen and discuss its occurrence in Lao PDR. The focal Laos specimen is similar in pelage color to those from northwestern Thailand, particularly on the dorsal and ventral surfaces of the body, gliding membrane, face, and tail. The cranio-dental characters (bullae and dental patterns) are also similar.
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