The first breeding of Fea's Treefrog - Rhacophorus feae at the Leningrad Zoo with account of the species.
by Anna A. Bagaturova, Mikhail F. Bagaturov (corresponding author, email: [email protected]), “Department of Insectarium and Amphibians”, Leningrad zoo, St. Petersburg, Russia
Abstract. The success of first captive breeding of the giant species of rhacophorid arboreal frog Rhacophorus feae in amphibian facility in Leningrad Zoo (Saint-Petersburg, Russia) has been described. Their natural history data, conservation status, threads, natural predators, morphology including size discussion, prophylactic and medication treatment; issues of adopting of wild adult specimens, keeping and captive breeding in zoo’s amphibian facility were described; features of breeding behavior stimulation, foam nest construction, rising of tadpoles and young frogs of other rhacophorids in comparison with hylid treefrogs’ species were discussed. Keywords. Rhacophoridae: Polypedates, Rhacophorus maximus, R. dennysi, R. annamensis, R. orlovi, Kurixalus odontotarsus, R. feae: natural history, conservation status, threads, description, thread pose, Vietnam, Thailand; captive management, adaptation, breeding, nest, tadpoles, froglets, veterinary; feeding, proper housing, Hylidae, captive management, raising; Leningrad Zoo.
Genus Rhacophorus H. Kuhl and J.C. van Hasselt, 1822 comprised for over 80 species (Frost, 2011, with later additions). Every year new species of rhacophorid frogs described from the territories of Vietnam, China, Cambodia and other countries of southeastern Asia for last decades (Inger et al, 1999 a, b.; Orlov et al, 2004, 2005 etc, see: References section for others). Some species of Rhacophorus also referred to as Polypedates, Aquixalus and Kurixalus according to different authors (Orlov and Ho, 2005, Fei et al, 2005, Yu et al, 2009, Frost, 2011, etc). The type species is Rh. Moschata Kuhl & van Hasselt, 1822 (= Hyla Reinwardtii Schlegel, 1840). According to different points of view taxon Rhacophoridae Hoffman, 1932, which genus Rhacophorus belonging to subfamily Rhacophorinae, for several times on different research data (mostly molecular: Wiens at al, 2009, Li et al, 2008, Li et al, 2009) was included into family Ranidae as a subfamily (Rhacophorinae) or distinct family (Bossuyt and Roelants, 2009). Here we accept the position of Orlov and Ananjeva, 2007 and latter authors by positioning this taxon in family status belonging to neobatrachian clade Ranoidea. Species account of Rhacophorus feae (Boulenger, 1893): Types: MSNG, BMNH. Type territory: “Thao, northern Burma (=Myanmar)”: 19° 23' N, 96° 54' O, 1300 m-1400 m a.s.l. Also referred to as: Polypedates feae (auct. n.) Distribution: South China (Yunnan: Mengla, Hekou and Pingbian Counties), Lao People's Democratic Republic, Myanmar (Karen Hills), North Thailand, Vietnam (North, Central (1 locale) and South (1 locale)).
Picture 1. Adult male of Rhacophorus feae with froglet sitting on its head. Photo©Mikhail F. Bagaturov Conservation status and threads. Natural predators. IUCN (Red List) status: Least Concern (LC). That shall be changed at the opinion of authors of this article due to an information massive analyzed during the study and research for the species (see below data). Their status in Thailand is listed as "near threatened" [Nabhitabhata, J. & T. Chan-ard, 2005], because of just the few areas where they are known from. Greatest threats would most likely come from habitat destruction, local climate change by deforestation of unprotected land and rising temperatures from global climate change would definitely threaten their presence in Thailand. It is listed as “endangered“ in Vietnam also due to a limited locality known [Red Datа Book of Vietnam, 2007]. The most known population in Sa Pa suffers from urbanization due to a tourists development of the region as well as deforestation and habitat loss. Species of snakes Amphiesma sp. found on feeding on eggs in the foam nests [Cota, pers. comm., 2010] as well as maybe other species of snakes and groups of reptiles and also amphibians predating on tadpoles, froglets and smaller frogs. It is supposed that they live most of their adult life high up in the trees which they come down from only during the breeding season, thus, adults do not suffer much from predators (collecting by locals for food in breeding pools was and is maybe still one of the major threats). Observation in nature: for the last 20 years in fact it is known from Thailand (Doi Lang, Fang District, Chiang Mai Province [Cota, pers. comm.]; Mae Hong (Pa Sue Falls); Phu Luang, Loei), North (Lao Cai and Lai Chau provinces) and South (Kon Tum province; Chu Yang Sin National Park, Dak Lak province) Vietnam [Nikolai Orlov, Roman Nazarov, Nguyen Thien Tao, Thomas Ziegler, Jody Rowley]. Natural history of R. feae in Vietnam (by Orlov and Ananieva, 2007; by Nguyen Thien Tao, pers. comm., 2010) Inhabits mountain range between 1200-2000 m above see level (on northern territories); found mostly in primary forests and may be found near the villages; breeds in May-June (Vietnam) and July (Thailand) on quiet reaches of mountain streams, ponds densely covered with bamboo, banana trees and large Aroid plants. Calling males usually occupy plant leaves, big branches and rock surfaces around the pool at a stand of 1.5-3 m. Most breeding pools are small but deep and allows adult specimens to hide in which they do readily under any thread.
Picture 2, 3. Habitat of Rhacophorus feae in Thailand (on the left). Photo©Mihael Cota. Breeding pool at base of the peak of Doi Lang. Nests are visible. Photo©Mihael Cota
Nests usually constructed not high above the pools (less than half a meter) on rocks, bamboo and bush branches, sometimes near the water on the ground. There is also data according that breeding season lasts in Vietnam from April to November [Nguyen T. Tao, pers. comm]. In the southern area (Chu Yang Sin National Park) they inhabit montane forests above 1500 m a.s.l.
Natural history of R. feae in Thailand (by Michael Cota, pers. comm., 2010) Known from high elevation in montane forests over 1000 m a.s.l., for example: base of the peak of Doi Lang, the second highest mountain in Thailand, Doi Inthanon, Thailand's highest mountain [Nabhitabhata, J. & T. Chan-ard, 2005], etc. In their habitat it has been found in sympatry with Tylototriton verrucosus, which also prefers cooler temperatures, in a number of known localities. Breeding site found at the base of the peak of Doi Lang, Thailand's second highest mountain, with mating aggregation of 5 specimens at a spring fed pool, less than 4m x 4m (See: Picture 2, 3). There were three or four nests already present on foliage hanging over the pool (July).
Description. Size discussion. Very large, presumably the largest species of arboreal frog of world fauna (see below for size discussion). Named by George Albert Boulenger in 1893 after great Italian naturalist and zoologist Leonardo Fea (1852 - 1903) who was the collector of the type specimen in the year 1888 among other material brought from his expedition in Burma (Myanmar) [Boulenger, 1893]. Common names known for the species: Fea's (Giant) Treefrog; Thao Whipping Frog; Brown-Folded Treefrog.
Picture 4. Rhacophorus feae, adult male (on left) and Rhacophorus dennysi, adult female (bluish overall coloration is due to CB origin of specimen), pictured for comparison on palm. Photo©Mikhail F. Bagaturov
Coloration (see: Picture 1, 8) is of different shades of green or dark-brown which mostly dependent on the species' mood and activity in connection with lights, humidity, etc. In the breeding season, the males’ skin develops a scabrous structure overall and the rostrum becomes elongated in the form of a beak-like extension (same is known in males of R. dennysi, but even more prominent). Skin of the female always stays smooth during all parts of the year. Sexual dimorphism in size is also represented like in most rhacophorid frogs (see: Table I). Two large longitudinal ridges of yellowish-brown color alongside lateral fold of the head in adult are characteristic of the species that differentiate it from other giant treefrogs – Rhacophorus dennysi found in the same areas in South China and Vietnam whose ridges are of the same color as the body, but not so intensively developed (see: Picture 4). Body is a bit depressed, not as rounded as in other closely related species. Fea’s treefrog also uniformly colored, as opposed to its close relative, R. dennysi, which has different colored spots on the lateral and dorsal part of the body (rusty, blue or white depending on population they are originated from the wild). Size. Specimens kept in Leningrad zoo: - largest male, c. 12.1-12.3 cm, - female, c. 13.8-13.9 cm.
Picture 5, 6. Average size male specimen of Rhacophorus feae from amphibian facility (on left) and female in terrarium at the Leningrad zoo, pictured near the ruler. Photo©Mikhail F. Bagaturov
Regarding the size of the biggest arboreal frog, there are different opinions and data known from different sources. Records listed for a female Litoria infrafrenata for 13.9 cm TL as the largest (supposed to refer to a female: authors’ point) [Tyler, 1992].
Source Male size, in Female size, in Source Male size, in Female size, mm mm mm in mm Bagaturov M.& Bagaturov M.& Bagaturova A. c. 112 - 128 c. 138 – 139 Bagaturova A. c. 98-98,5 c. 102-128,5 (measurements made on (3 specimens) (1 specimen) (measurements made on (1 specimen) (5 specimens) live specimens) live specimens) Nguyen Thien Tao 99,4 - 104,7 122,3 Nguyen Thien Tao 60,8–98,9 106,1 – 120,1 (2 specimens) (1 specimen) (6 specimens) (4 specimens) Orlov N.&Ananieva N. 83,4 – 106,5 103,6 – 120,1 Orlov N.&Ananieva N. 96,4 – 128,2 97,2 – 132,1 (10 specimens) (6 specimens) (25 specimens) (25 specimens)
Table I. Size data on Rhacophorus feae. Table II. Size data on Rhacophorus dennysi. Same data (14 cm) distributed in different Internet sources, like Wikipedia, etc. Measurements were made in the collection of the Zoological Institute of the Russian Academy of Sciences of another very large arboreal frog Rhacophorus (Polypedates) dennysi [Orlov&Ananieva, 2007] reports maximum of 128,2 mm for males and 132,1 mm for females; although, anecdotal data like 18-20 cm [Evgeny Rybaltovsky, 2003] and even larger sizes are also known for this species (in trade, not proven). Our above presented measurements make Rhacophorus feae the biggest tree frog of World’s fauna, which only L. infrafrenata can match. The collective size specimens’ proven data showed in Tables I, II. Captivity sources known. Trade. Known just from several collections in captivity. Successful keeping (over 1 year) known only from: i) 3 collections in Russia: - Leningrad zoo, St. Petersburg (by “Department of Insectarium and Amphibians”) - Zoocom Ltd., St. Petersburg (by Evgeny Ribaltovsky) - ZooFond, Moscow (by Rustam Berdiev) ii) 1 collection in Latvia: Riga Zoo (by Ilze Dunce) iii) 1 collection in Thailand: at Chulalongkorn University in Bangkok [Cota, pers.comm.] Many farm bred young specimens (originated from Hanoi Amphibian station, Vietnam where they are bred outdoors in great numbers with most offspring released to nature (Froglog, 2009), and poss. other sources from the country) as well as WC subadult to adult frogs traded to private collections and institutions, but most of the frogs were lost due to bad conditions they usually arrived in (hardships during transport), skin diseases and improper husbandry, and yet not any of them were bred. Adaptation of frogs in captivity. Rhacophorus feae is a very difficult species to adapt to captivity. There are several reasons for that. i) poor condition of the specimens due to transportation (dehydration, skin diseases etc.) ii) need of low temperatures in keeping conditions iii) nervous (especially in adult females) nature.
Picture 7, 8. Average sized adult male Rhacophorus feae on a palm (on left), group of three adult males (see color difference among frogs) in terrarium of Leningrad Zoo. Photo©Mikhail F. Bagaturov
To avoid the above listed problems, provide them with a large heavily planted terrarium with a deep layer of water and many hides (underwater and arboreal), which is needed for the frogs to adapt. Adaptation may take several months to over a year, especially longer in females. It is also very good to cover 2 or 3 of the terrarium walls with black paper or other material overall to make frogs feel more secure. No day lights or artificial light sources should be used for them for the adaptation period. With some time, after 6 months or so, some males may adapt well enough to be handled with care (see: Picture 7), but in our experience, this is not the case with females.
Keeping and breeding experience in Leningrad Zoo (Dep. of Insectarium and Amphibians) Here I will describe the success of the Department of Insectarium and Amphibians of Leningrad Zoo in adopting, keeping and breeding these beautiful giants of the tree frog’s world. The Department of Insectarium and Amphibians is a relatively new department of the zoo of the city of Saint-Petersburg (Leningrad Zoo) was established in the Year of Frog, 2008. Since that time, the collection has grown to over 80 species of different amphibians of all 3 orders. A number of species have been bred, like: Paramesotriton laoensis, Notophthalmus viridescens, Dendrobates tinctorius, Trachycephalus resinifictrix, Rhacophorus annamensis, R. orlovi, Kurixalus odontotarsus, Theloderma corticale, T. asperum, T. stellatum, T. bicolor.
Picture 9, 10. Terrarium to maintain for adaptation and keeping of a group of adult Rhacophorus feae at Leningrad Zoo (on left), adult male in the terrarium. Photo©Mikhail F. Bagaturov
Rhacophorus feae is one of the species which the zoo planned to breed since having possibility to got adult specimens. Developing the breeding technique for this species will allow breeding of some other large rhacophorid species, like Rhacophorus dennysi, R. duboisi, R. dugritei and some others. In the beginning of September 2009, a group of 5 adult frogs were donated to the zoo by a private person. They were brought from Vietnam (Sa Pa population which is believed to be the most successful population so far, at least in Vietnam). After the 1.5 months of acclimatization and quarantine, as described in the Adaptation of frogs in captivity chapter, a pair was identified and given to Evgeny Ribaltovsky (Zoocom Ltd.) for further husbandry and breeding. Among the remaining group of three, all were after some time identified as males. During the year 2009-2010, males were found calling many times. They produce loud low single calls resembles the bark of the big dog. It was noted the call was more intensively made during the fall of the temperature in the room (especially at night time when decent drop of temperature in the room to 12 C recorded). Picture 11. Amplectant pair of Rhacophorus feae in terrarium at Leningrad zoo. Photo©Mikhail F. Bagaturov
They were housed in a very large vertical terrarium (150 cm high x 80 cm x 60 cm) filled with water to a level of 30 cm, several large tree trunks and halves of bamboo, as perches. Several large leafed artificial plants were placed to form arboreal hides for frogs (see: Picture 9). Average room temperature was 18-21 C during the warm period and 15-16 C during the cold period of the year. They were fed exclusively with imagoes of house crickets (Acheta domestica) as all other food sources (locust, mice, Dubia and Death-headed roaches) were rejected. In late September 2010 a pair of adult frogs was obtained from another private keeper in Moscow (presumed to be from the same population from Vietnam). During the quarantine, a male was found to develop a keratoleucoma on one of the eyes. When it was separated from the female, it was cured using a complex medication on the basis of known formula (see Bagaturov, 2011 a, b), with addition of 1 tablet of 0,25 Trichopol (Meyronidazole, Flagyl) and 0,25 Terbinafine (Lamisil) used the same way mixed in the same solution. This complete solution of 3 medications used successfully in order to prevent further diseases in a newly arrived rhacophorid frogs at the quarantine and also to treat them against different hard diagnostic disorders. This period, the temperature of the amphibian room, where the male was kept, as well as the lone female in the separate terrarium, was maintained at an average of 16° C during the day with night drops to 14-12° C. On 12th December 2010 after acclimatization considered being in good condition and gain some decent weight fed well within the month, the female was placed into the terrarium with the group of males which were active during these days and calling on regular basis as the temperature dropped greatly. On 14th December, a male was found in amplexus with another male, which produced "release calls" (which is similar to regular call but shorter and of lower sound). The same evening in the terrarium, an amplectant pair was found (see: Picture 11). In the morning of 15th December, a foam nest built the previous night was found. It was placed on the terrarium wall above 25-27 cm from water level (see: Picture 12, 13). Nest parameters: 16 cm high x 14 cm width x 10 cm deep (in the deepest place). The egg mass was uniformly distributed in the nest. The eggs appeared yellow with a 0.4 mm diameter (those seen on the surface). Those eggs found were not developed and though not to be fertile.
Picture 12, 13. Foam nest of Rhacophorus feae in terrarium at Leningrad zoo. Picture on left showing ruler for measurement. Photo©Mikhail F. Bagaturov
In the evening of 18th December, part of the nest (lower part, 1/3) was removed into a separate container and placed above the water (floated) (=Group I). In the early morning of 19th December, the first tadpoles with yell-sacs were found to have fallen into the water and actively moving in Group I (see: Picture 14). The container was replaced outside the cold room at constant temperature 23-23.5 C. Another part of the nest was taken and placed into the 2d container left in the parents’ room (= Group II) under the lower temperatures. The remains of the nest were left in the parent's room for incubation, to let the tadpoles fall into the water during the manual misting of the terrarium (=Group III). In Groups II and III, tadpoles were found to be developed, as well. A total of ca. 400 larvae emerged from the nest; however, it was very difficult to count the tadpoles in Group III. On average, 65-70% of the eggs deposited in the foam nest were believed to be fertile. Raising of tadpoles. During the day of 19th December, tadpoles felt from the nest in all three groups, but those in Group I, kept at a higher temperature, yell-sacs were already dissolved and gills were developed, unlike those in groups I and II (see: Picture 15). From 21st to 22d December, all tadpoles emerged from the nest. Tadpoles of Groups I and II were removed and placed into larger containers. Aquarium compressors were used for water aeration since 19th December. On 22d December 2010, tadpoles in Group I already showed no gills. Aquarium fish flakes were dropped into the water for feeding. As it was expected, tadpoles in Group I, kept at higher temperatures, developed faster than those of groups II and III left in the cool room. In the following weeks, tadpoles of Group I were actively feeding and increasing their size rapidly, unlike their siblings of groups II and III. On 23d December 2010, tadpoles in groups II and III start to feed (see: Picture 16). The next two days (24th-25th December) rapid enlargement in size of 3 times the growth in tadpoles of Group I was noted. They were feeding very actively for 2-3 times per day. No such level of growth was presented in groups II and III, feeding rate was also rather slow.
Picture 14, 15. Developed eggs and tadpoles of Rhacophorus feae into the foam nest (on left) and emerged larvae showing yell-sac and gills. Photo©Mikhail F. Bagaturov
On 15th January, tadpoles of Group I were placed into the larger tank after noting several of them appeared to have deformed, curled tails. At this stage, tadpoles of groups II and III start to reach closer size of those in Group I growing rate of which are not that rapid like it was noted first days. On 26th January, the development of fore limbs was finally recorded for several tadpoles in Group I, which was already seen in nearly half of them on 30th January (none in groups II and III). First development of fore limbs in tadpoles of Group I was observed on 5th February 2011 and the first metamorph emerged on 7th February 2011. Since that time, they started metamorphosing each day, rising in numbers: The same time in the whole group I, one can observe tadpoles already having just fore limbs. On 14th February 2011, there were already 30 froglets counted passing metamorphosis (see: Picture 17). After this date, each day 10-14 froglets emerged from the water. On 20th February, only 25 tadpoles were remaining, which passed metamorphosis within close to a week. It shall be noted that no any sign of leg development still were in groups II and III at the time. Several metamorphs emerged in bad condition, with leg deformities. No cannibalism was observed among tadpoles as it is known for many other anuran tadpoles (pers. obs. by authors). Tadpoles of groups II and III showed the same rate of growth and development. First, fore limbs were noticed in both groups on 4th March 2011.After 1 week, all tadpoles of Group I were metamorphosed. Development of front legs started in both groups equally on 17th March 2011 and the first froglets emerged in both enclosures on 21st-22d April. The mass metamorphosis in both groups happened from 26th April to 4th May 2011. The only difference between those groups was the late metamorphosis in the parent’s enclosure: last two froglets emerged on 2d June 2011 and 14th June 2011, respectively. Several froglets with leg deformities were also found among groups II, III.
Picture 16. Tadpoles of Rhacophorus feae on day 3 feeding on fish food. Photo©Mikhail F. Bagaturov
In general, the development of tadpoles from active feeding stages in Group I lasted 3 months, the same period for tadpoles in groups II, III was within half a year (see Table III).
Date of the event Stage of development Group I Group II Group III 19-22 December 19-22 December 19-22 December Emergence from nest 2010 2010 2010 26-30 January 4 March 2011 4 March 2011 Development of fore limbs 2011 5-6 February 17 March 2011 17 March 2011 Development of front legs 2011 7-27 February 26 April – 4 May 26 April – 4 May Metamorphosis 2011 2011 2011
Table III. Group data for the development of Rhacophorus feae tadpoles till metamorphosis. Raising of young frogs. All young frogs were raised in standard hand-made terrariums 30х28х45 (WLH) cm of size parameters furnished with 1-2 pots of climbing Phillodendron spp., Dieffenbachia picta and/or Dracaena sp.). Several branches made of bamboo or oak were placed to provide more climbing area, which they preferred over the glass walls (same with adult specimens unlike many other rhacophorid frogs which utilize wall surfaces for day resting and hiding). The bottom of the terrarium was make by a thin layer of peat Sphagnum sp. moss which was kept constantly wet to maintain the proper humidity regime, as well as a spraying twice per day in the morning and late afternoon was provided. UVB-bulb (ReptiGlo 2,0) used for lighting (it is important to provide UVB light to raise healthy rhacophorid frogs, in our experience), as well as regular day light bulbs making a 12/12 hour day/night cycle. The temperature level stayed within a 24-26 C (both, day and night) fluctuation; although, periods for higher temperature (27-28 C) during the day time happened due to the inability of controlling the non-isolated corridor facility. These higher temperatures caused some immediate and further deaths in young frogs; although, it is possible these conditions are stimuli for outbreak of some non-recognized disease which leads to numbers of loss among young frogs, always showing signs of convulsion.
Picture 17. Metamorphs/ froglets of Rhacophorus feae before re-housing into terrarium. Photo©Mikhail F. Bagaturov
They were kept in groups by 50-60 frogs under the following feeding regime: - each day - every other day within the month after metamorphosis; - 3 times per week from second to sixth month; - 2 times per week after 6 months, same like adult frogs. The diet of juvenile frogs consistent of house cricket larvae of appropriate size, although frogs after 6 months of age able to feed on imago crickets. Turkistan roaches Blatta (Shelfordella) lateralis was added occasionally each week with one of the feedings (not regularly). Each time the crickets were dusted with vitamin-calcium powder prior to feeding. No cannibalism was observed among young frogs just as published data before [Langerwerf et al, 1995] as it is known for some hylid species (Trachycephalus resinifictrix, in press). Growth rate of young frogs. To our surprise the growth rate of this species is very extensive as opposed to other closely related species we have experienced to raising, such as Rhacophorus maximus. Froglets, emerged at an average size of 2 cm SVL, increased near twice their size in the first two month, intensively growing further until reaching 5,5-6 cm of total length at the age of six months (control measurement made for several young frogs in Group I on 13th August 2011) and 4-4,5 cm for 3 month old frogs (same date of control measurements for frogs of Group II, III). With the noted growth rate, we expected the rapid growth of the frogs to possibly reach adult size in 1.5 years as we have experienced with the close relative species - Rhacophorus dennysi (unlike 3 years for the same species by Langerwerf et al, 1995); although, the size difference would be more prominent in groups, due to sexual dimorphism known in species.
Conclusions. Rhacophorid treefrogs growing principles discussion. Here we also want to discuss some of our observation made during the frog maintenance. It is interesting to note the observation of 2 strategies in young frogs of Rhacophorus feae of which one so-called “parachuting behavior” is a characteristic for rhacophorid frogs in general [pers. obs. by authors], as it is observed in many “flying” species we have like: Kurixalus odontotarsus, Rhacophorus annamensis, R. orlovi, which young frogs demonstrated even when they landed on floor, and another one we had observed only before in Rhacophorus orlovi - the thread pose considering to be acting as a defensive behavior described for adult specimen of R. feae in the wild [Le & Rowley, 2010]. Another point we would like to discuss is the remarkable rapid growth rate and a characteristic of growing in young frogs of 2 large species of rhacophorid frogs – R. feae and R. dennysi comparing the same for their other closest relatives which they share the same group in a Bayesian tree (so-called “dennysi-group” or “maximus-group”) with several other species among Rhacophorinae [Guohua et al., 2009] – R. maximus (two different “types”, possibly species) which we also raise in our facility, as well as some other larger rhacophorid frogs, with their requirements. Raising average to large species of Asianc treefrogs of subfamily Rhacophorinae is very difficult [Rybaltovsky a, b, 1999]. They grow rather slowly with cases known of regular loss of nearly whole broods and only reaching adult size in captivity at 3 years or more [our data]. The same situation is exists with another giant treefrog found in Vietnam and other SE Asiatic countries - R. maximus. On the contrary, such species like Kurixalus odontotarsus and Rhacophorus orlovi, also bred and raised by authors [in press], showed rapid growth rate reaching maturity at 1 and a half year of age or even less time in males (by vocalization).
Picture 18, 19. Group of young frogs of Rhacophorus feae at the age of 3 months (on left), and young frog at the age of 6 months. Photo©Mikhail F. Bagaturov
Knowing all these data, one can suppose the slow growth rate of such giants, like R. feae and R. dennysi, but our experience allows us to assert that the situation is quite different and it is possible to raise healthy frogs closer to adult size at the age of 1.5 – 2 years. There are four main factors which make it possible at our experience: use of the UVB lights (i), regular diet (ii), optimal housing of groups of growing frogs and their timely re-housing (iii). i) It is worth describing the value of UVB lights in order to assimilate Vitamin D3, Calcium and Phosphorus in animal organisms; although, there is a massive amount of different specialized literature issued on the topic. The only point we want to note is that none of the Hylid species of frog we have raised in captivity from young frogs (Agalychnis callydrias, Litoria caerulea, Trachycephalus resinifictrix, T. nigromaculatus etc.) had a strong need for these lights. But yet again, it is nearly impossible to raise healthy rhacophorid frogs, for example, Rhacophorus maximus and R. annamensis without it. ii) A lot is known about diet using for growing anurans in captivity. Crickets and cockroaches have mostly been used as starting feeding objects for treefrogs. They are often powdered with vitamin-calcium supply before feeding to animals. When frogs are growing, usually same objects used, but of larger size the same way. It is also widespread that adult frogs are fed on pinky mice, in addition to a main crickets-roaches diet. From our experience, when raising rhacophorid treefrogs, it is important to make changes and add new objects at the right time, since frogs are growing. Thus, we have good results in raising Rhacophorus annamensis for the first time, by changing their diet in offering pinky mice when the body size of the frogs allows us to do so. The same method is also used to successfully grow R. dennysi to adulthood. With some time, specimens which start to consume pinky mice start to grow and reach adult size; specimens that did not accepted mice experienced some deficiency resulting in osteopathology and prolapse of the cloaca, all which cause illness and ultimately death. iii) It is also very important to maintain the proper ratio of number of the young frogs with the terrarium capacity (optimal housing conditions). For the different species of treefrogs, it may vary a lot, as their offspring can metamorphosed at size of ca. 5 mm, like Rhacophorus orlovi [our data, in press.], as well as 25 mm (R. feae). Thus, the same number of frogs needs different housing capacities. It is not effective to keep smaller number of frogs in a large terrarium, as well as in a cramped one. The space should be optimal for frogs that they should not be overcrowded and at the same time will not experience any problems catching the food. It is wise to place a lot of thin branches into enclosures; unlike most hylid treefrogs, rhacophorid frogs hardly utilize terrarium walls preferring to hide, rest, as well as hunt on leaves of plants, large pieces of bark or branches. Doing this, you increase the enclosure volume by being allowed to house a larger number of young frogs and allow them to utilize terrarium space more intensively. When frogs grow, one should realize that they need a bigger enclosure to properly grow (this is well-known in raising aquarium fishes). One may also notice an obvious of young frog size when it is re-housed into larger tank. Improper housing will also readily result in further deaths of animals. The above factors should be together in use for raising healthy rhacophorid treefrogs. We had some lost in young frogs, as well as developed deformities in tadpoles and froglets development as maintenance provisions were not ideal due to technical imperfections of our facility and space deficiency, which leads to congested housing of young frogs. We are lucky to have found the trigger of stimulation by rapid temperature reduction for breeding of this species, as well as we expecting this to also be sufficient and necessary in breeding some other species of montane rhacophorids, inhabiting cold forests of high elevation. By our suggestion this was confirmed by Evgeny Ribaltovsky, who was one of the first in breeding Rhacophorus dennysi in Russia, also pointed out the stimulation to breeding of this giant treefrog species by lowering housing temperatures [Evgeny Ribaltovsky, pers. comm] unlike the known published data [Langerwerf et al, 1995]. We are also happy to be raising near 100 young frogs of this species in the zoo which we are ready to exchange and distribute to the institutions who may be interested to maintain the proper conditions of raising this real gentle giant of treefrogs. Acknowledgment. Authors would like to express their deepest respect to Michael Cota (Natural History Museum, Thailand) and Nguyen Thien Tao (Vietnam National Museum of Nature of VAST, Hanoi, Vietnam) for the advices on the article and sharing the data of the species in Thailand and Vietnam including their own in-situ observations, pictures and data, Dr. Sergei Ryabov (Tula Exotarium, Tula, Russia), Prof. Natalia Ananjeva and Dr. Nikolai Orlov (Zoological Institute, St. Petersburg, Russia), Roman Nazarov (Moscow State University, Moscow, Russia) Evgeny Rybaltovsky (Zoocom ltd., St. Petersburg, Russia), Rustam Berdiev (Zoofond ltd., Moscow, Russia), Ilze Dunce (Riga zoo, Latvia), Dr. Peter Janzen (Zoodirektoren, Duisburg, Germany) for their suggestions on the manuscript and information exchange during our research. Roman Parshkov, Pavel Vas’kov and Igor Dzharayan (Leningrad zoo, St. Petersburg, Russia), our friends Vadim Nozdruhin and Kirill Kravchenko (St. Petersburg, Russia) for providing the help with care of growing tadpoles and froglets, Dr. Peter Janzen (Duisburg, Germany) for his suggestions and corrections on a manuscript, as well as our colleges in Leningrad Zoo who had supported our work in the zoo.
References.
Amphibiaweb.org, account for R. feae.