Annual Cycles of Coat Changes, Antler Regrowth, and Reproductive Behavior of Sika Deer in Nara Park, Japan*
Total Page：16
File Type：pdf, Size：1020Kb
哺 動 学 誌(J.Mamm.Soc.Japan)10(1):1-7(1984) Annual Cycles of Coat Changes, Antler Regrowth, and Reproductive Behavior of Sika Deer in Nara Park, Japan* Shingo MIURA Department of Biology, Hyogo College of Medicine, Nishinomiya, 663 Japan ABSTRACT.- The annual cycles of coat changes, antler regrowth, and reproductive behavior of sika deer were studied in Nara Park. The grey-brown winter coat ap- pears in late August and October, and it is molted to reveal the red summer coat in early May and June. Males tend to molt earlier than females. Adult males cast their antlers in early March and the new antlers are fully developed by August. Their velvet are shed by early September. Younger males tend to cast later. Rutting occurs from late September until early March of the following year with a peak in October. Fawning takes place from mid-May until November with a peak in June. Gestation period is estimated to be 226-233 days. The information on the annual cycles of sika deer (Cervus nippon) is qualitatively incomplete and quantitatively undocumented. The purpose of this paper is to present detailed descriptions of the annual cycles of coat changes, antler regrowth, and re- productive behavior of sika deer in Nara Park. Study Area and Methods The field study was conducted at Nara Park, encompassing over 390 ha, in the central part of Honshu, Japan. Although the park is not fenced and the deer can move freely, most deer inhabit the flatter and open western half of the park, where the vegetation is predominantly Zoysia grassland sparsely populated with trees (mostly Pinus densifiora). According to a direct census carried out by the Nara Deer Fund in July, 1977, the deer population was 1,075. A total of 132 observations were made along established census routes all over the western half of the park at least four times per month from June, 1977 through October, 1979, and each lasted from 3.0 to 5.5 hours. Most data were collected between 0600 and 1700 hours. Deer were assigned to six age-sex classes; adult male (four years old or older), juvenile male (two to three years), yearling male, adult female, juvenile female, and fawn. A yearling male was considered to have become a juvenile on the 1st of May. In each observation, the number of males that cast their antlers and shed their velvet in each age class were counted. The number of deer that molted into summer or winter coats were counted for each sex, too. Molt stages were easily determined visually from the following four stages; l) red summer coat with white spots, 2) molting * This work was supported in part by a Grant-in-Aid for Special Project Research on Biological Aspects of Optimal Strategy and Social Structure from the Japan Ministry of Education, Science and Culture. 2 哺 乳 動 物 学 雑 誌 Vol.10,No.1 coat with long light red hairs, 3) smooth grey-brown winter coat, and 4) molting coat ruffled with hairs that stand up. Antler lengths (from cornet to the most distal tip) of males were estimated to the nearest 2 cm by sight. These data were combined into three age classes for analysis. To measure reproductive performance, I observed breeding behavior and counted the number of conceptions at each observation during the rut. In addition, the number of new borns during the fawing season were counted. The shoulder heights of the fawns were measured to the nearest 2 cm by sight at the closest distance pos- sible to estimate when they were born. Fawns whose shoulder heights were less than 40 cm were considered to have been born within the last few days of the census (KANA- MORI,unpublished data). Careful inspection of the behavior of fawns and mothers, especially movements, maternal protection, and resting postures in hiding places, provided clues for estimating the approximate age of fawns (INOUE& KAWAMICHI 1976). A large number of deer could be identified individually from distinctive marks, such as, natural nothecs on their ears, scars, or metal eartags, which permitted detailed examinations of molting, antler casting, shedding velvet, and antler regrowth of individual animals. Results and Discussion Molt With some exceptions, molting began at the neck and outer part of the upper limbs, continued along the back, and then proceeded onto the flanks and belly; this sequence was also observed for red deer (WATSON1967, RYDER 1976). The molt varied greatly between individuals. Fig. 1 shows the percentage of animals in stages 1, 2, or 3 and 3, 4, or 1 in the two molting seasons. For the fall molt, the first animal in stage 2 was found on the 24th of August and the molting of all animals was com- pleted on the 15th of October, 1978. A detailed molting schedule for males was not obtained from late September onward because many males were caked with mud from their wallowing activities. For the spring molt, the first animals in stage 4 were found on the 1st of May, 1979. By the 26th of June, all animals had red summer coats. Thus, the duration of the fall and spring molt for all animals is about two months. The time necessary to complete a molt for each individual, which may be influenced by their nutritional condition, was one to two weeks. For both molting seasons, males were earlier than females; also observed for red deer (RYDER1976). However the timing of the molt for males was not related to age. It was noticeable that the molts of fawns' birth coats coincided with their mothers' molts irrespective of their birth dates. There were no significant variations in the molting schedule between 1977-1978 and 1978-1979. Antler casting Antler casting is associated with the initiation of renewed antler growth (WALDo & WISLocKI 1951, Goss 1963, 1983). Observations on some known adults showed that they cast their antlers of each other within four days. Fig. 2 shows the casting 1984”N3ŒŽ Annual Cycles of Sika Deer in Nara Park 3 Fig. 1. Timing of fall and spring molt in 1977 and 1978. Fig. 2. Casting of antlers in each age class in 1978. schedule for each age class; it is apparently related to age: adult males cast their antlers as early as the 5th of March, and as late as the 5th of June. It is generally accepted for cervids that the oldest males cast earliest and the younger ones later (Loss 1963, MCCULLOUGH1969, BEHREND& MCDOWELL1967). Generally, yearl- ings are the last to cast: only 22 % of the yearlings had cast their antlers by the 1st of May, whereas all two years old and older males had cast theirs by that date . There were no marked differences in antler casting between 1978 and 1979. 4 哺 乳 動 物 学 雑 誌 Vol.10,No.1 Fig. 3. Growth curves of antlers in each age class in 1978. Vertical line represents standard error. Antler regrowth Following the casting of the old, new antler buds appeared on the stump of the pedicle within a week. As with casting, the oldest males began regrowth earliest, and the youngest last. Fig. 3 illustrates the mean length of antlers for each age class and shows that the adult and juvenile growth curves are sigmoid in shape, whereas the yearlings' are linear. Antlers reached their full length with about a one month time lag between the age classes: August for adults, September for juveniles, and October for yearlings. Although larger antlers grew faster, growth duration for all age classes was approximately same. After one month for the final stage of matura- tion, the velvet of antlers was shed. Shedding velvet Fig. 4 shows the shedding schedule for each age class; yearling males shed their velvet later than adult males. All males shed in about two months. Observations on individually identified animals showed that the length of time for shedding velvet ranged from four to 10 days. By violently thrashing bushes and rubbing tree trunks, velvet was shed from the tips of the tines to the base. All adult males shed their velvet before the fall molt, but juvenile and yearling males shed during or after the molt. Timing of the rut Dramatic behavioral changes occurred in males as the rut approached: they became progressively more intolerant of other males and frequently interacted ag- gressively with other males. Male groups began to break up as older males started to wander off to their rutting areas (MIURA 1983). Then, each dominant male established a mating territory and tried to herd females to form a harm. MIURA (1984) reported that patterns of seasonal variation of male-male interactions were 1984 3 , Annual Cycles of Sika Deer in Nara Park 5 Fig. 4. Shedding velvet in each age class in 1977, Fig. 5. Frequency of copulations per 10 days for the 1977-1978 and 1978-1979 ruts. similar to patterns of sexual interactions, which increased rapidly after mid-September, peaked in early October, and then gradually declined. Although some sexual interac- tions were observed in the pre-rut from late August to mid-September, actual copual- tion was never observed. The first copulation occurred in late September when females entered estrus. In the final pahse of sexual interaction, a male would suddenly rise up on his hindlegs, clasp the female with his forelegs, and mount her. Usually, several mounting attempts transpired before copulation occurred. Generally, it is easy to distinguish copulation from mounting by behavioral differences. Copulation 6 哺 乳 動 物 学 雑 誌 Vol.10,No.1 Fig.