14/01/2018

So you have an amphibian…

What is an amphibian?

Amphibians are classed into three orders:

  • The Anura, which includes frogs and toads
  • The Caudata, which includes salamanders and newts
  • And the Gymnophiona, which includes caecilians (limbless, worm-like creatures)

All three of these groups are characterised by being reliant on water and ectothermic (‘cold-blooded’), and unfortunately, approximately 40% of all amphibians are in direct danger of extinction.

What makes amphibians different to mammals?

Mammals are fairly recent additions
to the evolutionary chain
Amphibians are an ancient group of animals on the evolutionary chain
Endothermic (warm blooded) Ectothermic (cold blooded)
Have haired skin Have bare and moist skin
Can adapt to every continent/ environment Are restricted to moist environments
Have four-chambered hearts Have three-chambered hearts as well as additional ‘lymph’ hearts
Rely largely on their lungs for respiration Some can breathe through their skin, gills, lungs and via a ‘buccopharyngeal’ route
Have kidneys that can conserve water when they are dehydrated Have a limited ability to conserve water and rely on a constant water supply

What type of amphibians do we see at The Unusual Pet Vets?

At the Unusual Pet Vets we see two types of amphibians: frogs and axolotls. The most common frog species we see are the Australian green tree frog and occasionally motorbike frogs. Both can make good pets, but are not great as ‘starter’ or first time pets, as they have very specific husbandry requirements.

Frogs
The species of frogs seen at The Unusual Pet Vets are primarily nocturnal,
which allows them to avoid the hottest, driest times of day. Some of the frogs,
such as the green tree frog are long lived, reaching up to 20 years of
age and up to 14cm in length.

Diet
An essential part of keeping frogs is understanding their dietary requirements. Both adults and juveniles are insectivores and eat a range of live insects in the wild. Appropriate insects include crickets, cockroaches, earthworms, silkworms, slugs, moths, mealworms and wax worms. Care must be taken with mealworms and wax worm portions however, as these insects are very high in fat and overfeeding can lead to significant health problems.
Most insects should be treated with calcium via gut-loading and/or dusting prior to being fed. This is to prevent against nutritional diseases such as metabolic bone disease which results from chronically low calcium diets. This condition is very common in captive frogs.
Feeding of rodents and mince meats should generally be avoided in tree frogs (or only given occasionally), as these animals cope poorly with high protein diets and can develop kidney disease.
In terms of how much to feed, adults should be fed 10-20% of their body weight each week, in 2-3 separate feedings (i.e. offer insects every 2-3 days). Juvenile frogs should be fed more frequently (every day or so depending on their size), but with smaller amounts.
Water access should be provided at all times, but simply using tap water may cause your frog to become sick. Tap water can contain chlorine and heavy metal additives that can be dangerous to frogs, and the level of these chemicals can be decreased (or removed) with water conditioners (available at good pet stores) or by placing the water in a shallow dish in direct sunlight for a day.

Husbandry
As arboreal animals, tree frogs require different levels in their enclosure,
which can be achieved with fake plants, bamboo, tree branches or PVC pipes.
The walls of the enclosure are best made from glass or Perspex, and where
possible it is good to have the roof of the enclosure made from a safe
breathable mesh (materials that rust or can injure the frogs should be avoided)
as this allows ventilation. UV lights come in a large variety of sizes and shapes, but are essential for captive frogs. Appropriate UV lighting allows frogs to metabolise calcium, and without a good source of UV frogs can develop metabolic bone disease. A frog should be able to bask within 20cms of the UV light for it to be effective, and the UV globe changed every 6 months to ensure your frog is receiving enough light (over time the UV output of the globe decreases).
In terms of what temperature is best for your frog, the water temperature should generally be kept between 20-26oC for most species. The thermal gradient temperature in the cage should generally be  between 180C (at the cooler end) to around 35oC at the hottest end, however every species is different. By having a temperature gradient the frog can then self-regulate its own temperature. Any heat sources – whether you use a heat mat or heat lamp – should be placed on a thermostat to prevent dangerous fluctuations in the temperature from occurring. Water temperature can be maintained with an external water heater and filter system.
Another important aspect of your frog’s environment is the humidity. Humidity can be increased by using air pumps or bubblers for smaller cages, but often sprinklers, waterfalls and living plants are required and recommended for larger enclosures. The humidity for most species should be kept between 50-70%. If there are no living plants or filtration system being used, the water in the cage should be changes weekly. This can be extended to fortnightly if appropriate filtration is present.  Small percentage (e.g. 20%), regular water changes are better than large percentage, infrequent changes.
As for the substrate (what type of flooring to use), there are a range of products available. In general, avoid those substrates that are abrasive and/or ingestible. Some good substrates include sphagnum moss, foam rubber, large rocks or moist paper towels (for smaller enclosures). 

Axolotls
Wild axolotls (ambystoma mexicanum) are only found in one lake system in the world based in Mexico, and therefore are classed as an endangered species. Fortunately, Axolotls have become popular pets worldwide, and the captive population is now larger than those that exist in the wild. They can reach 10-15 years of age (although reports of individuals living over 20 years is not unheard off) and reach lengths of 30cms.
Axolotls are unusual amphibians, as they never develop a terrestrial (land-based) form. Normal amphibians such as frogs lay eggs, which then develop into tadpole and mature into frogs for adult life. Axolotls essentially stay as ‘tadpoles’ for their entire life, but are still able to mate and breed in this ‘larval’ form. This is known as neotony. Interestingly, some axolotls have been known to develop into salamanders when exposed to certain thyroid hormones and iodine compounds, but not all axolotls have this ability.

Diet
Axolotls are carnivorous predators whose diet ranges from insects to small fish. As axolotls cannot chew their prey, in captivity they rely on humans to chop their food into small pieces so they can swallow their food whole.
Like other amphibians, axolotls are prone to develop calcium deficiencies on insect-based diets, and therefore any insects fed should be supplemented with calcium and/or a multi-vitamin. The insects can also be gut loaded which helps to increase their nutritional value. Ideally, an adult axolotl should be fed an amount of ‘several mouthfuls’ every second day.
Note: Axolotls are adapted to eat moving prey; many axolotls will require training or ‘wiggling’ of any still prey items before they recognise this as food.

Husbandry
As axolotls have external gills, they have a requirement to be submerged in water at all times. Drying out or desiccation of their gills can cause axolotls to suffocate, and for this reason, handling axolotls outside of their tank environment should be kept to an absolute minimum.
Unlike more tropical amphibians, axolotls are adapted to temperate water conditions and water heating is often not required. The tank water should be maintained between 17-18oC ideally however they will generally tolerate 14-20oC . The pH should be around neutral (6.5-7.5). The water depth should be at least as deep as the length of your axolotl.
Axolotls should generally be housed separately to each other, as they will frequently attack other members of their species.

Life cycle
Axolotls are oviparous or egg laying amphibians. Both males and females will reach sexual maturity at 12 months of age, but will not reach their full adult size until 2-3 years of age. Breeding between the adults is triggered by a sudden drop in water temperatures combined with a good amount of food on offer. The male and female can be observed dancing together before the male releases packets of sperm into the water, which the female will then take in and produce up to 600 fertilised eggs. It is not uncommon for these eggs to be eaten, but if they survive for 2-3 weeks, the eggs will hatch and release larval axolotl young.

Summary of Axolotls and the Green Tree Frogs

Characteristic Green tree frogs Axolotls
Ambient temperature – Max 
Ambient temperature – Min
34C
18C
N/A : 100% water borne
Water temperature 24-26C 15-19C
Ultraviolet light (UV) Require a low UV output 12 hours a day Require a low UV output 12 hours a day
Humidity 50-70% N/A: 100% water borne
Average lifespan 15-20 years 12-15 years
Can they be housed with others? Yes In some cases
How often should I change the water? Change 20% of the water every week Change 25% of the water every week
Diet Gut-loaded calcium insects Worms, insects, fish
Feeding – Juveniles
Feeding – Adults
Every 1-2 days
Every 3-7 days
Daily
Every 3-5 days
Sexual Maturity 8-12 months 12-18 months
Reproduction Oviparous (egg-laying) Oviparous (egg-laying)
License category in WA 2 None