Yukiko Matsuura

Monitoring ovarian cycle and conception by fecal progesterone analysis in sika deer

The ovarian cycle and conception of sika deer were studied to reveal factors responsible for delayed conception. Concentration of progesterone in feces from 12 female Hokkaido sika deer (Cervus nippon yesoensis Heude, 1884) was measured during the mating season in 2000. The cyclic pattern of fecal progesterone synchronized with estrous symptoms, which could hence be interpreted as indicating ovarian cycle. All observed females ovulated by 14 October. However, during the early mating season, females did not permit copulation at ovulation, and the length of luteal phase following ovulation without estrus was 9.8 ± 4.6 days (5–24 days). Most females conceived at the first copulation, which were confirmed by progesterone profiles that was sustained at a high level after the copulation. This indicates the presence of a functional corpus luteum, a state of pregnancy. Thus, some females had repeated ovulation without copulation several times, creating a 3–4 week variation in the timing of conception. But some females conceived very late in the mating season after the repetition of ovulation and copulation.

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.

Dystocia in free-ranging sika deer Cervus nippon under food limitation

Graduate School of Agriculture, Hokkaido University, Sapporo 060-0809, JapanIn understanding the mechanism of population dynamicsof large mammals, it is essential to clarify the mortalityfactor. For ruminants, birth size is a major factor of neo-natal survival because smaller neonates are more suscep-tible to exposure (Haughey 1980; English and Mullery1992) and vulnerable to predators (Singer et al. 1997).Birth size is commonly related to maternal body sizewithin and across species (Clutton-Brock 1991). Thefetus/neonate-mother proportion may be a consequenceof developmental or morphological constraints (MaynardSmith et al. 1985). For example, it is well known thatfetomaternal disproportion (FMD) causes dystocia, oftenresulting in high fetal/neonatal mortality in domesticruminants (cattle, Johnson et al. 1988; Schwabe and Hall1989; Noakes 1997; West 1997: sheep, McSporran andFielden 1979; Thomas 1990; Dwyer 2003). However,dystocia in wild ruminants has been scarcely reported indetail. This is partly because dystocia may rarely occuras a consequence of natural selection toward optimalbirth size (mass) for mother and offspring (Clutton-Brock 1991), and/or dystocia may be simply difficult todetect in the field. In fact, neonatal mortality in prong-horn Antilocapra americana was caused partly bydystocia (1.8%) but mostly by trauma (61.8%) due topredation (Dunbar et al. 1999). Also, dystocia causedmortality of adult females (<1%) in Swedish roe deerCapreolus capreolus, but the major causes were trau-matic injuries, starvation and pneumonia (Aguirre et al.1999). However, in animals whose growth and maturesize are restricted by environmental factors such as foodlimitation (e.g. Fowler 1987), FMD may occur fre-quently and be a cause of mortality. In this paper, weexamine the occurrence of dystocia in sika deer Cervusnippon under severe food limitation and searched theincidence of FMD.

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 Variation of Activity Pattern in Sika Deer (Cervus nippon) as Assessed by Camera Trap Survey

Abstract. Ungulate populations such as deer and wild boars have been expanding in range and increasing in number throughout many areas of the world. Regulation of these overabundant populations is urgently needed. For an effective culling program addressing these overabundant populations, it is essential to have information on the activity pattern of animals. To determine the factors affecting seasonality of daily activity pattern in sika deer, we studied deer activity through camera traps on Nakanoshima Island, Lake Toya in Hokkaido, Japan, where human disturbance is low. We estimated activity pattern during four time periods (dawn, dusk, day, and night), and evaluated the effects of weather conditions on activity pattern (camera trap rate) for each period. Deer activity at dawn, dusk and night showed clear seasonal patterns, with peaks in September, while the activity pattern during the day was constant in all seasons. The activity at dawn and dusk tended to be higher than that at day during July–October and July– November, respectively. Although the activity of sika deer may be influenced by weather condition, there was no seasonal consistency. Our study reveals that human disturbance might decrease diurnal activity and increase nocturnal activity.

Accessory corpora lutea formation in pregnant Hokkaido sika deer (Cervus nippon yesoensis) investigated by examination of ovarian dynamics and steroid hormone concentrations

Generally, sika deer conceive a single fetus, but approximately 80% of pregnant females have two corpora lutea (CLs). The function of the accessory CL (ACL) is unknown; moreover, the process of ACL formation is unclear, and understanding this is necessary to know its role. To elucidate the process of ACL formation, the ovarian dynamics of six adult Hokkaido sika deer females were examined ultrasonographically together with peripheral estradiol-17β and progesterone concentrations. ACLs formed in three females that conceived at the first estrus of the breeding season, but not in those females that conceived at the second estrus. After copulation, postconception ovulation of the dominant follicle of the first wave is induced by an increase in estradiol-17β, which leads to formation of an ACL. A relatively low concentration of progesterone after the first estrus of the breeding season is considered to be responsible for the increase in estradiol-17β after copulation.

Robustness of adult female survival maintains a high-density sika deer (Cervus nippon) population following the initial irruption

Abstract Context. Irruption of large herbivore populations is characterised by three distinct phases: (1) an exponential increase in population to a peak abundance; (2) a population crash; and (3) a second increase to another population peak, typically lower than the first peak of abundance. However, there has been little study of age- and sex-specific factors that affect the post-initial irruption interactions with food sources. Aims. We aimed to investigate annual survival rates of sika deer (Cervus nippon Temminck, 1838) in the sequent irruption of a population on Nakanoshima Island, Lake Toya, Japan, with a chronically high density during the period 2002–12. Methods. Survival monitoring data were obtained for 219 individuals (93 males and 126 females) using radio-collars. Annual survival was quantified, and related factors, i.e. deer abundance and winter severity, were determined by model selection using Akaike information criterion values. Key Results. The results showed that annual survival rates across sexes and age classes (fawn, yearling, prime-aged, old) decreased with increasing population density, snow depth and winter precipitation. Winter severity had a greater effect on adult survival than density regulation. Nevertheless, female adult survival was maintained at a high level, with a mean of 0.84 (95% CI: 0.80–0.88). Key conclusions. Robust survival rates for adult females might contribute to the maintenance of a high-density sika deer population in the post-initial irruption. Implications. We suggest that in the absence of predation and hunting, sika deer population is not able to self-regulate to the density level that avoids an irreversible impact on plants.