Japanese Journal of Herpetology 16(4): 117-128., Dec. 1996 (C)1996 by The HerpetologicalSociety of Japan Breeding Activity of a Stream-Breeding Toad, Bufo torrenticola HIROSHI TSUJI AND TAKEO KAWAMICHI Abstract: The breeding activity of the stream-breeding toad (Bufo torrenticola) was studied in Mie Prefecture for three years from 1990 to 1992. Aggregation in the main pool, which was intensively investigated, occurred explosively in early April for 12- 14 days. The oviposition period was 5-11 days in the main pool, and 14-17 days in the entire length of stream. First, many toads appeared on a particular section of the migration path, on their way to the stream. In about 300 individuals captured in the main pool, the males: female ratio was 2.0-2.4:1. The daily number of toads found in the main pool showed the normal distribution pattern with a sharp peak in the middle of the breeding period. Toads appeared to be most active during the nighttime. The onset of migration to the stream was affected by soil temperature rather than by air temperature; during the three years, maximum soil temperatures were 10.0-11.0℃, and minimum soil temperatures ranged 8.5-9.0℃ . Oviposition activity in the main pool in 1991 and 1992 occurred in the later half of the breeding period, when the minimum water temperature was above 10.0℃. Breeding activity, however, was not strongly associated with weather conditions, probably because breeding is performed underwater. Key words: Bufo torrenticola; Stream-breeding toad; Migration; Breeding Activity; Oviposition The genus Bufo has a wide distribution cover- (Maeda and Matsui, 1989). Its tadpoles have ing temperate and tropical regions and is com- poorly developed external gills, a well-developed prised of more than 200 species (Duellman and oral disk, a short tail, and a poorly developed Trueb, 1986). Most Bufo species breed in lentic tail fin, all of which are probably adaptive to waters, such as ponds, marshes, and temporary torrential environments (Matsui, 1975; Iwasawa pools (e. g., Blair, 1972; Beebee, 1983), whereas and Saito, 1989). Information on the breeding species breeding in lotic waters, such as streams, ecology of this species, however, is largely lack- are extremely rare. Only a few species are so far ing (Matsui, 1976; Tsuji and Kawamichi, 1996). known as stream breeders (Tevis, 1966; Blair, In this paper, therefore, we examine the 1972; Zhao et al., 1989; Yang, 1991; Lips & breeding activity of B. torrenticola in natural Krempels, 1995). Although many researchers conditions, focusing on the following three have reported the reproductive ecology and aspects: (1) migration to a breeding stream, (2) mating behavior of still-water breeders (reviewed temporal patterns in the breeding activity, and by Wells, 1977; Arak, 1983), there are few cor- (3) influence of weather conditions on the responding data for stream breeders in Anura, breeding activity. except for a few species (Metter, 1964; Dole and Durant, 1974; Kusano and Fukuyama, 1987, MATERIALS AND METHODS 1989; Fukuyama et al., 1988; Fukuyama and Study site.-This study was conducted along Kusano, 1989, 1991). a 1500m stretch of the Higashimata-dani, a Bufo torrenticola is a large mountain toad branch of the Hirakura River (34°27'N, whose breeding and larval development occur in 136°15'E; 440-600m elevation), in the Misugi rocky torrents in central Japan (Matsui, 1988; Forest of Mie University and is located 60km Maeda and Matsui, 1989). This species has southwest of Tsu City, Mie Prefecture, central several morphological differences in both adults Japan. In this typical rocky stream, riffles are and tadpoles from B. japonicus, the Japanese 2-5m wide and 15-30cm deep, and the pools are still-water breeding common toad. Bufo torren- 5-10m wide and 0.5-2m deep. The stream ticola has an indistinct tympanum, longer limbs, banks are rocky, shaded by tree foliage, and the and elongated skin on the back in breeding males stream runs through conifer plantations and natural deciduous broad-leaved forests. A Accepted 1 Oct. 1996 forest trail runs along the stream. 118 Jpn. J. Herpetol. 16(4). 1996 The "main pool", at an altitude of 500m, was period. All toads detected were marked, their the breeding pool with the greatest number of locations were noted on maps with the time of egg-strings in the study site every year (Tsuji and capture, and they were released outside the Kawamichi, 1996). This pool was elliptic in fence. The census on the trail was conducted shape, and was 12m×7m in size in 1990. It also in 1992 when the cloth fence was not set up. was deformed by a typhoon in the autumn of The temporal change in the number of toads 1990 to 16m×7m thereafter. The maximum was intensively monitored in the main pool; water depth ranged from 60cm to 90cm during a census was taken 1-3 times every day and the three breeding seasons. Its rock base is par- 3-7 times every night throughout the three tially covered with rocks of various sizes, gravel, breeding periods. During each census, the and sand. A sloping waterfall with a height of number of single males, single gravid females, 10m flows into this pool. The current is relative- and amplexed pairs were counted, individual ly fast in the central part of the pool, but the marks were identified, and unmarked individuals shores are quiet. The right bank of this pool is a were marked. In 1991 and 1992, toads appear- rocky cliff, and the left bank is a bushy slope ing in the main pool were captured as much as towards the trail, which is about 20m above the possible; the percentage of the marked toads in main pool. the last census on each day was about 80%. In Observations. -This study was carried out in 1990, however, the capture rate of toads was three consecutive breeding seasons between 1990 much lower. To examine the movements of and 1992. The study period in the main pool marked toads from the trail to the stream and was between 1 and 21 April 1990, between 23 between the main pool and downstream to it, March and 20 April 1991, and between 25 March censuses were conducted from the main pool to and 20 April 1992. In 1991 and 1992, the study 200m downstream (the lowest major breeding included the entire breeding period in the main site), once in the daytime and once at nighttime pool, but in 1990 the survey in the main pool was every day throughout the breeding period in conducted only in the oviposition period. On 1991. almost every day and night during the study The days from the first to final emergence of periods, the main pool and the trail were regular- toads in the main pool were regarded as the ly investigated in order to detect toads. The breeding period, or the time of breeding activi- daytime and nighttime censuses were conducted ty. The days from the first to final oviposition in between 0700 and 1700 h, and between 1800 and the main pool and throughout the whole stream 0400 h, respectively. Observations at night were regarded as the oviposition period. The were made using a 4.5-volt headlamp and/or a cessation of oviposition in the whole stream 6-volt flashlight, neither of which appeared to was confirmed by counting egg-strings newly disturb the toads' behaviour. deposited every 1-2 days, after the breeding Toads were captured by hand or with the aid activity in the main pool ceased. The date of of a net. Captured individuals were marked by egg-laying was determined, based on the develo- uniquely toe-clipping them for permanent iden- pmental stages of the eggs and embryos (Iwasawa, tification and by attaching a waist band with a 1987). numbered tag for behavioural observations. Daily air temperatures, soil temperatures Both individuals of amplexed pairs were marked (20cm underground), and the amount of without separating the pairs; a numbered plastic precipitation during the study were obtained tag (5mm × 5mm) was stuck to their heads with from the Meteorological Station (513m eleva- cyanoacrylic glue (see Howard, 1988). All mark- tion) in this forest. The annual mean ed toads were released within 15 min at their temperature was 12.4℃, and the annual points of capture. precipitation was 2500mm. Water temperature In 1990 it was found that many toads at the in the main pool (30cm below the surface) was beginning of the breeding period appeared at a measured during every population census in particular part of the trail on the way to their 1991 and 1992. breeding sites in the stream. In order to capture the toads passing through the trail, a cloth drift RESULTS fence 60cm high was set up in 1991 on the Migration from trail to stream. -Bufo torren- stream side along 250m of the trail. A census ticola first emerged on a particular part (about on the trail along the drift fence was conducted 200m long) of the trail along the stream every 2-4 times every day and 2-5 times every night, year (Fig. 1). A few breeding toads were found more frequently at the beginning of the breeding higher than the extent of the drift fence, but no TSUJI AND KAWAMICHI-TOAD BREEDING ACTIVITY 119 FIG. 1. Left: the main study site (dotted) in Higashimata-dani. Current direction is from top to bottom . Right: movements of Bufo torrenticola between the trail and stream in 1991. Circles on the trail indicate marking points of single males: open circles were those males recaptured later in the main pool and solid circles are those recaptured at smaller points downstream.