Influence of Density and Climate on Population Dynamics of a Large Herbivore Under Harsh Environmental Conditions

ABSTRACT Dynamics of herbivore populations can be influenced both by density-dependent processes and climate. We used age-at-harvest data for adult female white-tailed deer (Odocoileus virginianus) collected over 23 years to estimate survival and reproduction by age class and to identify effects of environmental factors. The study population was located on Anticosti Island (QC, Canada), at the northern limit of the species' range; the population was at high density, and the landscape had scarce forage and abundant snow during winter. Despite severe environmental conditions, population growth apparently increased during the study; adult survival was similar to other populations, although reproduction appeared lower. Winter severity was not related to survival, but density affected adult female survival. Density at estrus was the main factor influencing reproduction of 2- and 3–4-year-olds and also affected reproduction of prime-aged females (5–9-yr-olds), but not of older females. Reproductive rate of younger females was influenced by environmental conditions in autumn, such as high density or snow conditions that limited forage availability. Reproductive success of 5–9- and ≥10-year-old females appeared dependent on spring conditions favoring high-quality forage, probably through effects on neonatal survival. Relative to other studies on northern ungulates, demographic processes in our study appeared to be more affected by autumn and spring climate, in addition to population density, than by winter climate. We thus propose that population density, as well as autumn and spring climate, should be considered in management strategies. Harvest data offered a unique opportunity to study forest ungulates, for which individual monitoring is rarely possible.     

Ungulate damage and silviculture in the Cansiglio Forest (Veneto Prealps, NE Italy)

The Cansiglio Forest, situated in the Veneto Prealps, is of particular naturalistic and landscape interest, going back to the times of the Most Serene Republic of Venice. Its long silvicultural tradition, which is now even more “near to nature”, remains unaltered. Over the last century there has been a considerable increase in the number of ungulates. This is partly due to prohibition of hunting since the beginning of the 20th century throughout the territory. It has therefore become necessary to survey forest regeneration, to ascertain whether deer pressure hampers silvicultural goals and also to investigate which factors are most involved. A review of management plans over the last 30 years identified areas in which regeneration is present, where transects were subsequently sampled. Inside every transect, all saplings (over 50 cm) were measured for diameter and height and monitored for degree and type of damage (browsing, debarking, fraying). Using the CART statistical method, the following key factors were singled out: species, proving that fir is the most frequently selected sapling; silvicultural system, clarifying that the regeneration of uneven-aged stands is more subject to damage; aspect, locating more damage in the southern and eastern areas, probably because they are more often frequented by deer. High densities of deer endanger fir survival, reduce biodiversity, and affect forest economy, limiting silvicultural choices, so that culling ungulate populations seems to be necessary.     

Correlations between feeding type and mandibular morphology in the sika deer

Morphological comparisons of the sika deer Cervus nippon mandible and molars were conducted between two (northern and southern) Japanese subspecific lineages and among local populations of different ('grazer' or 'intermediate feeder') feeding types. The northern lineage showed greater M₁ breadth, M₃ hypsodonty and mandibular corpus height than the southern lineage. Such differences were not observed between the 'grazer' and 'intermediate feeder' populations of the northern lineage. However, a northern population, which inhabits a particularly harsh environment (Kinkazan Island), had the largest values of relative molar size and hypsodonty, although this was not statistically significant. These results imply that, in the Japanese sika deer, the selective pressures acting on the current 'grazer' populations are not strong enough to bring out noticeable adaptive change in molar size and hypsodonty, but adaptive change in these traits may occur in an environment that promotes excessive molar wear, more than that seen in the current sika deer habitats of Japan. Combined with what is known of the Pleistocene history of the sika deer, we infer that the ancestral population of the northern Japanese lineage likely acquired their relatively larger and more hypsodont molars in an extremely harsh environment during the last or previous glacial periods.     

Seasonal changes in the dietary compositions of rusa deer in Pangandaran Nature Reserve,West Java,Indonesia

Information regarding the food habits of tropical cervids is limited. We studied the food habits of rusa deer (Rusa timorensis), a tropical cervid in the Pangandaran Nature Reserve, West Java, Indonesia. The faecal composition of the rusa deer collected over a year was analysed using microscopy of plant fragments. The results showed marked seasonal changes: in the rainy season, the rusa deer mainly fed on Cynodon dactylon, a lawn-like grass, which accounted for approximately 50% of the faecal composition. During the dry season, C. dactylon in the faeces decreased to approximately 20%, while the composition of fruits increased, suggesting that food conditions for the deer were better in this season. This pattern differs from that of temperate cervids which can feed on abundant plant leaves during summer but are forced to consume low-quality foods such as bark and dead leaves during winter.     

Transabdominal Ultrasound for Pregnancy Diagnosis in Reeves' Muntjac Deer

Reeves'' muntjac deer (Muntiacus reevesi) are a small cervid species native to southeast Asia, and are currently being investigated as a potential model of prion disease transmission and pathogenesis. Vertical transmission is an area of interest among researchers studying infectious diseases, including prion disease, and these investigations require efficient methods for evaluating the effects of maternal infection on reproductive performance. Ultrasonographic examination is a well-established tool for diagnosing pregnancy and assessing fetal health in many animal species^1-7, including several species of farmed cervids^8-19, however this technique has not been described in Reeves'' muntjac deer. Here we describe the application of transabdominal ultrasound to detect pregnancy in muntjac does and to evaluate fetal growth and development throughout the gestational period. Using this procedure, pregnant animals were identified as early as 35 days following doe-buck pairing and this was an effective means to safely monitor the pregnancy at regular intervals. Future goals of this work will include establishing normal fetal measurement references for estimation of gestational age, determining sensitivity and specificity of the technique for diagnosing pregnancy at various stages of gestation, and identifying variations in fetal growth and development under different experimental conditions.     

鹿科动物基因组学研究进展

鹿科动物是世界上最丰富的大型哺乳动物之一,在极北地区、热带地区和高海拔地区都有分布.中国占世界鹿科动物40％以上,是鹿科动物进化的主战场.鹿科动物除了具有反刍动物常见的独特表型特征外,更是进化出周期性再生新器官——鹿茸角.鹿科动物是研究生态学、行为学和进化生物学非常有价值的动物模型,特别是在研究哺乳动物器官再生方面具有...     

The role of genetics in chronic wasting disease of North American cervids

Chronic wasting disease (CWD) is a major concern for the management of North American cervid populations. This fatal prion disease has led to declines in populations which have high CWD prevalence and areas with both high and low infection rates have experienced economic losses in wildlife recreation and fears of potential spill-over into livestock or humans. Research from human and veterinary medicine has established that the prion protein gene (Prnp) encodes the protein responsible for transmissible spongiform encephalopathies (TSEs). Polymorphisms in the Prnp gene can lead to different prion forms that moderate individual susceptibility to and progression of TSE infection. Prnp genes have been sequenced in a number of cervid species including those currently infected by CWD (elk, mule deer, white-tailed deer, moose) and those for which susceptibility is not yet determined (caribou, fallow deer, sika deer). Over thousands of sequences examined, the Prnp gene is remarkably conserved within the family Cervidae; only 16 amino acid polymorphisms have been reported within the 256 amino acid open reading frame in the third exon of the Prnp gene. Some of these polymorphisms have been associated with lower rates of CWD infection and slower progression of clinical CWD. Here we review the body of research on Prnp genetics of North American cervids. Specifically, we focus on known polymorphisms in the Prnp gene, observed genotypic differences in CWD infection rates and clinical progression, mechanisms for genetic TSE resistance related to both the cervid host and the prion agent and potential for natural selection for CWD-resistance. We also identify gaps in our knowledge that require future research.     

Legal regulation of supplementary cervid feeding facing chronic wasting disease

The supplementary feeding of cervids is a widespread practice across the northern hemisphere. There are few studies, however, regarding the extent of feeding in space and time. There are adverse effects of supplementary feeding, of which the most severe are increased parasite and disease transmission. With the recent emergence of chronic wasting disease (CWD) among cervids in Norway, a legal regulation was issued that banned all supplementary cervid feeding. We quantified the spatial extent and intentions of feeding cervids across all of Norway using a questionnaire at the municipality scale. We also compared spatial extent of feeding before and after the feeding ban to shed light on the ability of regulations to control supplementary feeding. Supplementary feeding to increase winter survival and targeting roe deer (Capreolus capreolus) was more common (48.4% of the municipalities) than the feeding of red deer (Cervus elaphus; 20.5%) and moose (Alces alces; 7.4%). The main feeding period was January–March, but extensive feeding also occurred from November to December and in April. Reducing traffic accidents was also a motivation, particularly for the feeding of moose (14.5%), and this was the main motivation (86%) for public feeding. Among the 65.7% that responded, 53.3% reported they knew about supplemental feeding of cervids in their municipality. In the region with the first feeding ban, 80.2% of municipalities were feeding in 2015–2016 before the ban, which was reduced to 68.4% in 2016–2017 and remained at 68.4% in 2017–2018. In the remainder of Norway, 81.4% were feeding in 2015–2016, and 72.6% were feeding in 2016–2017, but after the ban, this increased to 78.6% in the harsh winter of 2017–2018. Our study highlights that regulations across broad scales may not be followed and that more spatially targeted regulations and increased enforcement are required for disease transmission to be more effectively combated. © 2019 The Authors. Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Ecological and behavioral correlates of coloration in artiodactyls: systematic analyses of conventional hypotheses

To test the generality of adaptive explanations for coat colorationin even-toed ungulates, we examined the literature for hypothesesthat have been proposed for color patterns exhibited by thistaxon, and we derived a series of predictions from each hypothesis.Next, we collected information on the color, behavioral, andecological characteristics of 200 species of even-toed ungulatesand coded this in binary format. We then applied chi-squareor Fisher's Exact probability tests that pitted presence ofa color trait against presence of an ecological or behavioralvariable for cervids, bovids, and all artiodactyls. Finally,we reanalyzed the data by using concentrated-changes tests anda composite molecular and taxonomic phylogeny. Hinging our findingson whether associations persisted after controlling for sharedancestry, we found strong support for hypotheses suggestingeven-toed ungulates turn lighter in winter to aid in concealmentor perhaps thermoregulation, striped coats in adults and spottedpelage in young act as camouflage, side bands and dark facesassist in communication, and dark pelage coloration is mostcommon in species living in the tropics (Gloger's rule). Whereaswhite faces, dark legs, white legs, dark tails, and white tailsdid not appear to assist in communication alone, legs and tailsthat were either dark or white (i.e., conspicuous) did seemto be linked with communication. There was moderate supportfor hypotheses that countershading aids concealment, that whitefaces are a thermoregulatory device, and that white rumps areused in intraspecific communication. There was weak supportfor spots in adults and stripes in young providing camouflageand for dark leg markings being a form of disruptive coloration.We found little or no evidence that overall coat color servesas background matching, that side bands are disruptive colorationdevices, or that white rumps help in thermoregulation. Concealmentappears the principal force driving the evolution of colorationin ungulates with communication, and then thermoregulation,playing less of a role.