Captive Propagation of the Japanese Pit Viper
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Japanese Journal of Herpetology 8 (3): 90-94. 1980. Captive Propagation of the Japanese Pit Viper, Agkistrodon blomhoffi blomhoffi Gerald MARZEC* ABSTRACT: I obtained a group of 5 Japanese pit vipers, Agkistrodon blomhoffi blomhoffi (2 males and 3 females), from a reptile dealer in New Jersey in June 1963 and kept them in captivity. One female bred annually from 1964 to 1967, a second female bred once in 1966, and the third female bred in 1966 and 1967. Of the 7 broods born in captivity, the number of young in each litter varied from 3 to 12 with a mean of 7.0. The conditions of light and temperature in the cages were as follows: in winter, 8 hours of light, with a temperature of 19-21℃ during the day and 13-15℃ at night; in summer, 16 hours of light, with a tem- perature variation of from 21 to 29℃; the light and temperature were gradually increased during the spring and decreased during the fall. INTRODUCTION The Japanese pit viper, Agkistrodon blomhoffi blomhoffi, is a common viviparous snake found on the larger main islands of Japan. Locally it is called the "mamushi". Regarding its breeding habits, Fukada (1962, 1972) has reported the size of litters born in captivity and the growth of captive-born young, but there seems to be no report in the literature of successive yearly reproduction of this species. I have kept a group of mamushis which mated and reproduced annually . In this report I record my observations on these events, together with a description of the conditions of housing and feeding. MATERIAL In June, 1963, I obtained a group of 5 mamushis from a reptile dealer in New Jersey. The group consisted of 2 males and 3 females. I identified these as Japanese mamushis on the basis of coloration and pattern. The total length of each specimen, measured in June, 1963, is shown in Table 1. All of the specimens were colored normally except for female No. 1, which had two dorsal stripes down the rear 20.5cm of the body. * 15 Goodwill Lane , Holbrook, N. Y. 11741, USA 90 Vol. 8, No. 3, 1980 91 Table 1. Total length of specimens measured in 1963. CONDITIONS OF CAPTIVITY 1. Housing The breeding group was housed in a cage measuring 1m×1m×64cm high. The cage was constructed of plywood with a glass door in the front. The plywood was coated with a layer of fiberglass resin. There was a pool 25.5cm×20cm×5.5cm deep, which served the snakes as a water dish and enabled them to soak themselves when they desired. The substrate was a pine bark mulch. There were numerous retreats formed by rocks, hollow logs, and artificial plants. 2. Lighting and temperature Variation in temperature was achieved by the use of heat tapes placed under one side of the cage. This allowed the snakes, to some extent, to choose a suitable hiding place at a preferred temperature. Lighting was achieved by the mounting of a Gro-Lux fluorescent bulb above the glass door. On each side of the Gro-Lux bulb there was a 60W incandescent bulb. All lighting fixtures were covered by a mesh screen to keep the snakes from coming in direct contact with the bulbs. The lighting fixtures and the screening were not visible when the enclosure was viewed from the outside. A yearly light cycle was maintained as follows. I used 8 hours of daylight during the winter months with the nighttime temperature between 13℃ and 15℃, and a daytime temperature of 21℃ with a cooler area of 19℃. During this 8-hour daily cycle I maintained a 30% level of humidity. There were times when some of the mamushis had to be soaked in gallon jars containing warm water to aid in shedding. This light cycle was gradually increased in the spring to 12 hours of daylight with a range in temperature between 18℃ and 26℃. At this time an 85% level of humidity was maintained by twice daily spraying the cage with a mist of water. During this cycle it was never necessary to soak the snakes to aid in shedding. The daylight cycle reached its maximum at 16 hours in the summer months with a temperature range between 21℃ to 29℃ and a humidity level of between 65 to 75%. In the fall the daylight cycle and humidity were both gradually decreased until the 92 爬虫両棲類学雑誌 prementioned winter levels were reached. DIET AND FEEDING All of the adult mamushis were fed on a diet of one dead mouse every 10 days. The mice were frozen and then defrosted to room temperature prior to feeding. Each individual was removed from the display cage to a ten-gallon aquarium for feeding. Both of the males and two of the females (Nos. 1 and 3) would take the mice directly from forceps. Female No. 2 would have to be placed in an aquarium with a retreat and left overnight with a dead mouse, as this was the only way she would accept food. All specimens when first obtained would only accept live mice, as long as the mice offered were not white. The snakes were then conditioned to take freshly killed mice, and were then fed them until they started to accept the defrosted mice. There were only two conditions under which this feeding schedule was deviated from. The first exception was when the snakes became opaque before shedding, when they sometimes skipped a feeding. The second deviation occurred during the 12-hour daylight period. I would construct an imitation rat nest with used rat litter in a retreat inside a ten-gallon aquarium. I would then place four or five, depending on their size, live suckling rats inside the "nest". Each mamushi was permitted to eat these four or five rats per feeding. OBSERVATIONS 1. Copulation and Birth The 5 mamushis were normally housed together. However, prior to the 12-hour daylight cycle the two males were removed for approximately three weeks and housed separately. Upon re-introducing the males to the display cage there was a marked increase in the activity of both the males and females. The 5 mamushis were normally very secretive and copulation was observed only once, on the evening of June 7, 1964. At 8:30 PM I observed male No. 2 actively pursuing female No. 1. The male finally overtook the female and with much dif- ficulty oriented himself, by way of spasmatic jerks, along the left side of the female. There was much disparity between the lengths of the two snakes and it took quite a bit of work for the male to finally align himself with his vent in line with the female's vent. When this was accomplished, his tail was wrapped around the female's, and her tail was raised. At this point I could not see the insertion of the male's hemipenis due to a log in my line of vision. I did not want to take the chance and move the log for fear that any distraction might disrupt them so much that they Vol. 8, No. 3, 1980 93 would discontinue their mating. Both specimens remained motionless for about 3 minutes, and then for an additional 2 minutes the male twitched until they separated. The young were all born at night and all at one time. There was no "holding over" of the young as I have observed in some other species. One example is found in ball pythons, Python regius: I have on one occasion observed a female of this species lay 5 eggs in one sitting, and then lay another 4 eggs 2 days later. 2. Juveniles The young were all colored similarly to the adults although the patterns were more distinct and the colors much brighter. The tails were bright yellow on all of the young. Female No. 1 had the largest total of young (34). Although aberrantly patterned all of her offspring were typically colored and patterned. Dates of birth, number of young, etc. are shown in Table 2. In 7 broods born in captivity, the number of young in one litter varied from 3 to 12, with a mean of 7.0. The young were housed individually in plastic shoe boxes. Paper towels were used as a substrate. A small water dish was included, along with a piece of bark under which the young spent most of their time. Ecdysis took place for the first time between five and ten days after birth. Feeding the young proved to be quite difficult. At first, all refused pink mice and small lizards. All but a few started to eat small hylid frogs and then gradually accepted Anolis and pink mice. A small number of the juveniles refused all food items offered and were force-fed pink mice. Of these, all but two began to feed on their own after two or three force-feedings. Tail luring was observed in the majority of individuals. It was observed about 50% of the time any food item was placed in the cage. Typically the young snake would be under the piece of bark provided, and when it detected movement, it would extend its tail out from under the bark and wiggle it. Table 2. Data on birth and young of the mamushi. 94 爬虫両棲類学雑誌 REFERENCES Fukada, H. 1962. Biological studies on the snakes IX. Breeding habit of Agkistrodon halys blomhoffii (Boie). Bull. Kyoto Gakugei Univ. B, 20: 12-17. Fukada, H. 1972. Growth and maturity of some Japanese snakes (Review). The Snake 4: 75-83.