Cynops ensicauda has a snout-to-vent length of 53-77 mm and a total length of 103-179 mm. Its dorsal surfaces are generally black or very dark brown and its ventral surface is orangish red. The soles of its feet are the same color as its belly. Some individuals may have stripes or splotches of the ventral color on the back or head. Many individuals, especially those living in sunny locations, have lichenlike blotches here and there on the back and tail. The significance of these blotches is controversial, as they can disappear if the animal is kept in captivity under conditions of low light (Goris and Maeda 2004).
C. ensicauda is similar in appearance to C. pyrrhogaster but C. ensicauda is somewhat larger and has a longer, more slender tail. C. ensicauda can also be distinguished by the light color on the soles of its feet (Goris and Maeda 2004).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Japan
Cynops ensicauda occurs on most of the islands of the Amami and Okinawa Archipelagos, but is not found further south. This species is partially terrestrial, living inconspicuously under leaf litter in both lowland and mountainous forests. However, adults frequently enter the water, especially in search of food (Goris and Maeda 2004).
Life History, Abundance, Activity, and Special Behaviors
Cynops ensicauda has a fairly long breeding season. Depending on rainfall, the season may start as early as October-November and continue until June of the following year, with a peak in January-March. When a rain shower starts, the animals migrate to a suitable body of water, which may be a large pond, a rice paddy, a slow stream, a swamp, or a large ephemeral puddle, but is always in or close to a forest. Males arrive first, then the females. Courtship and spermatophore retrieval is essentially similar to that seen in C. pyrrhogaster but with a lower success rate. There are always many more males than females, all vying for a mate and constantly interrupting the nuptial dance so that the rate of successful spermatophore retrieval is very low: it has been estimated at 2%. Eggs are laid singly in folded-over underwater vegetation, as in C. pyrrhogaster. When the breeding aggregation is dense, the females may lay their eggs at the water's edge or even in mosses outside the water. The eggs are frequently eaten by other newts, especially in the water, and by the snake Amphiesma pryeri. After hatching, only a tiny percentage of the larvae survive to metamorphosis. They are preyed upon by dragonfly larvae and by the larvae of the newt Tylototriton andersoni and are cannibalized by other larvae of their own species. Weather also plays a role in the low survival rate of larvae. Most of the breeding sites are ephemeral. If rainfall is insufficient, the ponds, paddies, and puddles dry up, and a whole season's cohort of larvae perishes. Larvae that survive will metamorphose in about 3 months.
Little is known of the life of this species after metamorphosis. On land it eats the eggs of the newt T. andersoni, snails, slugs, earthworms, and probably small insects. In the water it eats frog tadpoles, its own larvae and those of T. andersoni, snails, tubifex worms, etc. Adults can secrete a noxious poisonous substance from the skin. At such times, they may assume a coiled defense posture with the eyes tightly shut (Goris and Maeda 2004).
Trends and Threats
The once-teeming populations of C. ensicauda have declined alarmingly in recent years. There has been massive habit destruction, especially of breeding sites, because of land development. Large, voracious fish of the genus Tilapia have been introduced into traditional breeding ponds. Even where supposedly suitable forest habitat has been preserved, the construction of access roads with concrete drainage ditches often proves fatal. The animals wander about to forage on rainy days and tumble into the ditches, where they are baked by the sun when the rain ceases (Goris and Maeda 2004).
Chytridiomycosis may be a threat to this species. Wild C. ensicauda were found to have a relatively high prevalence of Batrachochytrium dendrobatidis (Bd), with 12 of 24 sampled animals (50%) positive for Bd (Goka et al. 2009). Four Bd haplotypes were found on C. ensicauda (haplotypes A, E, I, and W) (Goka et al. 2009).
Relation to Humans
Cynops ensicauda has been collected by the tens of thousands for the pet trade. Most of these animals perish because they are sold and treated as aquatic animals, whereas in actuality they are partially terrestrial (Goris and Maeda 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Subtle changes to necessary specialized habitat
Predators (natural or introduced)
Intentional mortality (over-harvesting, pet trade or collecting)
Goka, K., Yokoyama, J., Une, Y., Kuroki, T., Suzuki, K., Nakahara, M., Kobayashi, A., Inaba, S., Mizutani, T., and Hyatt, A. D. (2009). ''Amphibian chytridiomycosis in Japan: distribution, haplotypes, and possible route of entry into Japan.'' Molecular Ecology, 18, 4757 - 4774.
Goris, R.C. and Maeda, N. (2004). Guide to the Amphibians and Reptiles of Japan. Krieger Publishing Company, Malabar, Florida.
Written by Nichole Winters (nichole_winters AT berkeley.edu), UC Berkeley
First submitted 2007-02-15
Edited by Kellie Whittaker (2009-11-30)
Species Account Citation: AmphibiaWeb 2009 Cynops ensicauda: Sword-tailed Newt <http://amphibiaweb.org/species/4242> University of California, Berkeley, CA, USA. Accessed May 29, 2017.
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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 29 May 2017.
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