By Gary Miller
Known by a few common names; forest green tree frog, Japanese flying tree frog and Kinugasa flying tree frog, Zhangixalus arboreus is a charismatic yet rarely-seen frog in the hobby. It is endemic to Japan and found throughout the central and northern regions of the country. They are large, highly variable frogs, with some females reaching up to 9cm in length. Being a species that is rarely kept in the UK, it is likely that the following feature discusses the first-ever UK captive-breeding of the Japanese flying frog.
Making sure they don’t Croak it!
Because of their natural range, Z. arboreus make a great choice for a thermally robust species to keep in the UK. My 1.4 group inhabit a custom-built 100cm x 50cm x 100cm glass tank that is situated in my unheated conservatory, year-round. I do not supply them with any additional heat source, except for the small amount given off by the UV light, allowing them to experience a sheltered but varied range of temperatures, in line with what the UK has to offer. My group have experienced temperatures of nearly 40°C in the summer, down to 1°C in the winter with no issues.
For UV, I supply them with a 7% T5 bulb, offering them a UVI of around 3.0 on top of the leaves at the highest point in the enclosure. The duration of light/day is controlled by a smart timer that allows me to gradually change the daylight hours to match the daylight hours here in the UK, from my phone, wherever I am.
For décor, I use oak heartwood. Some of this is for the aesthetic more importantly, I have used this wood in many different enclosures, and it is incredibly durable when it comes to high-humidity enclosures and even full submersion in water. These are positioned securely around the enclosure to allow for climbing and jumping behaviours. They also allow the animals to transition across temperature, light and humidity gradients.
Live plants are a ‘must’ for tree frogs. They play a large part in regulating the humidity levels in the tank when they respire at night and release water. My adults sit at 50-60% humidity during the day and up to 80% at night, just with the use of live plants and no additional spraying.
I have planted two large paper plants (Fatsia japonica) because they are hardy plants that offer large leaves that are strong enough to support these heavy frogs and provide lots of cover. Décor should be all about choice and providing lots of little microhabitats of varying heat, light and humidity levels across the enclosure.
Their water provision is a large shallow dish that takes up almost 50% of the floor space.
I find plant pot saucers particularly good when looking for a cheap water dish that comes in lots of colours and sizes. This is half filled with mature water (tap water left to mature over 48 hours) and changed every day.
Japanese flying frogs are ferocious eaters and readily accept a range of invertebrates, both scattered and tong-fed. I mostly feed brown and black crickets, but occasionally offer locusts and cockroaches. They are fed twice a week and usually take 3-6 crickets each, depending on the time of year and breeding cycle. All live food is gut loaded and a small amount of calcium supplement is dusted on before feeding out.
Hibernation
As the days draw in and the temperature starts to drop below 10°C (usually in late November), the frogs slow down their feeding and start to hide away, tucking themselves into the nooks of the plants, fairly low down in the tank. At this point, I supply them with a deep soil and leaf litter substrate which they proceed to bury themselves in. They turn a very dark brown colour and become dormant, only popping out on the fairest days to rehydrate in the water before returning straight to the soil.
Throughout this hibernation, I offer no food and reduce the water dish size down. It can be nerve-racking taking your herp through hibernation, especially when they are dealing with temperatures just above 0°C. Furthermore, on the few occasions that you do see them, you could easily mistake them as dead, non-responsive brown lumps in a hollow of soil. But, this is a natural process that these hardy frogs have evolved to endure.
Come April, the temperature begins regularly rising above 10°C and they start to wake up and can be seen frequenting the water more regularly. At this point, I increase the water dish size back up, remove the substrate and start chucking in the occasional few crickets and check each day for their disappearance. Before long, the frogs get back to climbing to the tank’s heights and accepting live food from tongs again.
Breeding
In the wild, this species will breed with the coming of the rains from May to July, producing foam nests with hundreds of eggs inside. A bit of research showed me that precipitation and nest location were factors that contributed to the successful hatching of the tadpoles in the wild sites that have been surveyed.
With that in mind, I began spraying the tank every evening from the start of May and gave them all an extra feed each week. The male would occasionally chirp at this time and seemed to be staying around the water’s edge most of the time. It was time to build a rain chamber.
Although rain chambers are often created out of practical necessity, I felt it was important to offer the inhabitants choice within their enclosure. I carefully considered the placement of plants to offer areas in the tank where there was shelter from the rain and leaves with varying degrees of wetness. This allowed me to better understand what the frogs would gravitate towards when positioning their nests.
I went with a simple enough design of one square of tubing tied centrally to the top of the enclosure with a pump and filter attached. The plants were moved on top of mercenary brinks to either side of the enclosure. This allowed the rain to fall centrally and interact with only a portion of the leaves – some drenched, some lightly sprayed and some almost dry.
The bricks kept the plants out of the reservoir of water at the bottom of the tank. This artificial pool was about 8cm deep. There was no need to add a water heater like I have done for other species in the past as the mature water was stored in the conservatory and became naturally heated to around 18-20°C. The rain was set to come on for 20 mins at a time during the day around 3 hours apart and then at night, one long burst of an hour, controlled via my phone and a smart plug.
Almost immediately, this process encouraged the male to begin croaking. This was a stereotypical call but with tempo changes thrown in, almost like having someone laughing audibly in your house, day and night…for two months!
By the first evening, the male had latched on to a female in amplexus and for the next couple of days, switched partners. On the fifth day, I came home from work to find a large white foam nest, about the size of a fist, hanging from one of the leaves, over the water. Two days later, another one. The male proceeded to find each female in turn and do his thing.
The tadpole stage
The eggs are hidden in the middle of the foam. Small, cream-coloured spheres that, as they grow, begin to sink through the foam towards the bottom. It was not until day five that I saw movement. The odd flicker of tiny black tails let me know the nests were indeed fertile. On day seven I saw the tadpoles begin to breach the foam. Only a few tadpoles breached at first, but then with the timings of the rain, more and more. As the nest disintegrated the tadpoles surfed down the leaves into the water.
I moved the tadpoles into a nursery tank. Again, the water temp was kept around 18-20°C at around 8cm depth but with the addition of some cork pieces to provide cover, and pond weed to help clean and aerate the water. The nursery tank had a 2.4% T5 UV bulb and allowed for a UVI of 1.0 from the surface of the cork pieces.
Daily, I would take out about 5-10% of the water, removing the faeces and uneaten food from the bottom of the tank with a large pipette and then offering fresh food in its place. I tried several different feed types; lettuce, cucumber, and vegetable flakes, but none of it was taken. It was not until I tried spirulina tablets that sunk to the floor, that I started seeing them feed.
From the size of a bb ball to about the size of the end of your little finger, they grew steadily, and after 3 weeks they began to protrude their rear legs.
At five weeks, their body size started to shrink and front legs began to protrude from the body which now was taking on some green pigmentation. Over the next couple of days, they began absorbing their tails and started leaving the water and climbing up onto the pieces of cork. Their body shape and colour began to appear very much like miniature versions of their parents.
By six weeks, the froglets had absorbed their tails and were ready to start taking live invertebrate food. Considering the adults’ ferocious nature to feeding, I decided to start with offering 2nd moult crickets, gut loaded and supplemented. Feeding little and often is always a good bet with younger herps and with these, one cricket eaten is probably going to fill their tiny stomachs.
Something else to think about with froglets, that differs from adults, is their tolerance for humidity. Coming from a completely aquatic environment, they need their terrestrial environment to be humid, 80% + to begin with. Live plants, large, shallow water dishes, wet paper towels on the floor and regular sprays all help to achieve this.
The joys of Herpetoculture
Keeping this species has given me immense fulfilment and a chance to learn about a species I have never kept before, to hone in on the details of how to help them thrive.
For me, this is what keeping is all about. To keep a few species well, rather than many, whose care is substandard. I can see the “collector mentally” becoming a thing of the past. I personally hope that it does, for the hobby to continue and attitudes towards animal care for the animal’s sake, improves.