Effects of culling intensity on diel and seasonal activity patterns of sika deer (Cervus nippon).

Adaptive hunting management is commonly used for controlling the populations of overabundant large herbivores; however, induced behavioural changes can make the effective control of target populations difficult. However, few studies have compared the impact of different levels of hunting intensities on the activity patterns of ungulates before, during, and after a culling program. We investigated how different culling intensities affect the activity patterns of sika deer on Nakanoshima Island in Lake Toya, Hokkaido, Japan using camera-trap surveys comparing the period of treatment before, during, and after a culling program. We used the number of deer photographed per hour per camera as an index of activity. Sika deer showed consistent crepuscular activity patterns (i.e., dawn and dusk) during spring-summer and trimodal activity patterns (i.e., dawn, dusk, and midnight) in autumn throughout the study period. In response to increased culling intensity, the activity peaks shifted slightly towards the night. The shift towards nocturnal activity persisted during post-culling period. Understanding the changes in activity patterns in response to culling intensity could be used to facilitate population control and assist in establishing a night shooting program. Thus, wildlife managers should consider night shooting once hunting during day time has shifted the normal diurnal activity of deer to nocturnal activity.

Ecological Character Displacement in Non-Congeneric Frogs.

Character displacement is phenotypic divergence driven by competition (ecological character displacement) or reproductive interference (reproductive character displacement). Although previous studies have examined these phenomena separately, recent evidence suggests that reproductive interference can drive both reproductive and ecological character displacement, in that certain traits are related to both competition and reproduction. Thus, to evaluate the effect of competition, the effect of reproductive interference must be excluded. Here, we analysed ecological character displacement between non-congeneric frogs, which show little reproductive interference. Odorrana amamiensis inhabits the Amami and Tokunoshima Islands, Japan, whereas its non-congeneric competitor Babina subaspera inhabits the Amami Island. We tested three of the Schluter (2000) criteria for ecological character displacement: phenotypic changes in O. amamiensis between the two islands, phenotypic change related to prey preference, prey availability between the two islands. We demonstrated that the three criteria in Schluter (2000) were likely to be satisfied, indicating the occurrence of ecological character displacement in non-congeners without reproductive interference. Thus, we conclude that competition is potentially the main driver of this phenotypic divergence, and that non-congeners may be a suitable model for evaluating ecological character displacement in a variety of organisms, as the influence of reproductive interference can be excluded.

Comparison of Drive Counts and Mark-Resight As Methods of Population Size Estimation of Highly Dense Sika Deer (Cervus nippon) Populations.

Assessing temporal changes in abundance indices is an important issue in the management of large herbivore populations. The drive counts method has been frequently used as a deer abundance index in mountainous regions. However, despite an inherent risk for observation errors in drive counts, which increase with deer density, evaluations of the utility of drive counts at a high deer density remain scarce. We compared the drive counts and mark-resight (MR) methods in the evaluation of a highly dense sika deer population (MR estimates ranged between 11 and 53 individuals/km2) on Nakanoshima Island, Hokkaido, Japan, between 1999 and 2006. This deer population experienced two large reductions in density; approximately 200 animals in total were taken from the population through a large-scale population removal and a separate winter mass mortality event. Although the drive counts tracked temporal changes in deer abundance on the island, they overestimated the counts for all years in comparison to the MR method. Increased overestimation in drive count estimates after the winter mass mortality event may be due to a double count derived from increased deer movement and recovery of body condition secondary to the mitigation of density-dependent food limitations. Drive counts are unreliable because they are affected by unfavorable factors such as bad weather, and they are cost-prohibitive to repeat, which precludes the calculation of confidence intervals. Therefore, the use of drive counts to infer the deer abundance needs to be reconsidered.

Seasonal and Diel Activity Patterns of Eight Sympatric Mammals in Northern Japan Revealed by an Intensive Camera-Trap Survey.

The activity patterns of mammals are generally categorized as nocturnal, diurnal, crepuscular (active at twilight), and cathemeral (active throughout the day). These patterns are highly variable across regions and seasons even within the same species. However, quantitative data is still lacking, particularly for sympatric species. We monitored the seasonal and diel activity patterns of terrestrial mammals in Hokkaido, Japan. Through an intensive camera-trap survey a total of 13,279 capture events were recorded from eight mammals over 20,344 camera-trap days, i.e., two years. Diel activity patterns were clearly divided into four categories: diurnal (Eurasian red squirrels), nocturnal (raccoon dogs and raccoons), crepuscular (sika deer and mountain hares), and cathemeral (Japanese martens, red foxes, and brown bears). Some crepuscular and cathemeral mammals shifted activity peaks across seasons. Particularly, sika deer changed peaks from twilight during spring-autumn to day-time in winter, possibly because of thermal constraints. Japanese martens were cathemeral during winter-summer, but nocturnal in autumn. We found no clear indication of predator-prey and competitive interactions, suggesting that animal densities are not very high or temporal niche partitioning is absent among the target species. This long-term camera-trap survey was highly cost-effective and provided one of the most detailed seasonal and diel activity patterns in multiple sympatric mammals under natural conditions.

Immunohistochemical localization of steroidogenic enzymes in the testis of the sika deer (Cervus nippon) during developmental and seasonal changes.

Testicular steroidogenesis and spermatogenesis during developmental and seasonal changes were investigated in male sika deer (Cervus nippon), a short-day seasonal breeder, to clarify the physiological mechanisms for reproductive function. The immunohistochemical localization of steroidogenic enzymes (P450scc, P450c17, 3betaHSD and P450arom), spermatogenesis and cell proliferation were analyzed in the testes of fetal (164 to 218 days of fetal age), fawn (0 years old), yearling (1 year old) and adult (more than 2 years old) male sika deer. Three kinds of steroidogenic enzymes, P450scc, P450c17 and 3betaHSD, essential for the synthesis of testosterone were located only in the Leydig cells of the testes from the fetal period, and these localizations did not change during developmental or seasonal stages. Immunoreactivity for P450arom, a key enzyme converting testosterone to estradiol, was also localized only in the Leydig cells of testes but was also further limited to the testes of yearlings and adults. Seminiferous tubules had already formed in the fetal testes examined in the present study. Spermatogenesis started in yearlings and was more active in the breeding season. In the adult sika deer testes, the Leydig cells, which displayed immunoreactivities for steroidogenic enzymes, changed to have more cytoplasm in the breeding season than in the non-breeding season. Cell proliferation of Leydig cells was hardly observed in adult testes during seasonal changes. The present results suggested that sika deer testes start to synthesize testosterone from the fetal period, that seasonal changes in testosterone and estradiol syntheses are dependent on the quantitative variation of steroidogenic enzymes synchronized with the size of Leydig cells and that estradiol synthesized in yearling and adult testes makes a contribution to the initiation and recrudescence of spermatogenesis and spermiogenesis in the sika deer.

Detection of Rickettsia helvetica DNA from peripheral blood of Sika deer (Cervus nippon yesoensis) in Japan.

Partial nucleotide sequences of the citrate synthase and 17-kDa genes of Rickettsia helvetica were detected from peripheral blood samples of Sika deer (Cervus nippon yesoensis) in Hokkaido, Japan. Results suggest the presence of a rickettsiemia associated with R. helvetica. This is the first evidence of R. helvetica infection in Sika deer and indicates that this species may represent a potential reservoir host of R. helvetica in Japan.

Detection of Ehrlichia muris DNA from sika deer (Cervus nippon yesoensis) in Hokkaido, Japan.

Ehrlichia muris DNA was detected in the blood of sika deer (Cervus nippon yesoensis) by species-specific PCR based on the citrate synthase gene, which was shown to be more sensitive than species-specific PCR based on the 16S rRNA gene. Among 102 deer examined, one deer was positive. Deer may be a possible mammalian reservoir of E. muris.