The naked mole rat (Heterocephalus glaber) is undoubtedly one of the strangest animals in the world. It is natural that it has special requirements regarding keeping conditions. These predicted difficulties may be the reason why a lot of zoos are afraid of keeping them. However, this species is a good example of ‘good story animals’ – they are very interesting for the visitors as well as good subjects of zoo educational work. So, is it worth keeping naked mole rats? I am sure it is; they are not as mystical as we considered before.
Actually, according to the ZIMS database, at least 58 zoos keep this species worldwide, and there are many specimens in research institutes too. So, a lot of experience has been gathered in the past years, which could help us keep the species. In addition, there is a lot of literature available, I suggest reading first: David Wood, Raymond Mendez: Husbandry Standards for Keeping Naked Mole Rats in Captivity. In the following I try to complete the article with my personal experience too.
How large should the facility be? Naturally, it is not a traditional, open-plan exhibit; we should provide them an artificial burrow system, which is large and complex enough. It is suggested to build round (20 cm / 8 in diameter) or square (25x25x15 cm / 10x10x6 in) chambers which are connected with tubes (5 cm / 2 in diameter). Holes (6 mm / 1/4 in diameter) should be drilled into the tops of the chambers to provide ventilation. I suggest creating openable roofs for every chamber. The second most common question is how many chambers do they need? If you want to breed them, you should provide enough space for the following generations too. For a breeding group of 5-10 adults I suggest minimum 6 chambers.
It is suggested to use Plexiglas or PVC as materials; at the visitors’ side it is advisable to install double layers to reduce the effect of knocking. The thickness of the wall of the boxes is about 8 mm / 1/3 in – and yes, the mole rats can chew it. The burrow system should be a network of chambers and tunnels, but it could have one dead end chamber too (usually it will be the toilet). If there are skew tubes it is suggested to build in grating to their bottom part, as a staircase. Pinewood shavings, cornhusk, grasses and paper towels are possible nesting materials. Sand and soil are not suggested because they make the chambers difficult to clean.
It is very important that the enclosure’s temperature range must stay between 26-31 °C / 79-88 °F. Higher or lower temperatures for extended periods may result in death. If there is a temperature gradient in the exhibit, the animals can choose the optimal place. The humidity level of the chambers should be maintained between 30-50%. Higher values (80% and more) have been recorded in the wild, but too low for an extended period is not healthy for them (causing ‘dry skin’). During transport the temperature should be between 23-30°C / 73.4-80 °F. In cold weather it is suggested to use an egg incubator or a warm bottle in a Styrofoam box.
Direct sunlight (or strong UV light) should also be avoided. It is suggested to use weak red lights (LED) in the chambers and tubes. The naked mole rats are almost blind; they can only perceive flash or other strong direct sources of light. Mole rats are very sensitive to sound which will affect normal behaviour and the successful rearing of offspring. Some zoos use radios playing 24 hours a day for desensitizing the animals. They can be very sensitive to knocking and vibrations, especially when there are babies. However, according to my experience, they can adapt well to this disturbance. During the first reproductions a separation wall was used in front of the exhibit for 2-3 weeks, but later they did not require it.
The habitat should be spot cleaned daily by removing old food and spoiled substrate. The entire habitat should be cleaned with mild dish soap every 2-4 weeks. The toilet chamber has an important role in maintaining the olfactory identity of the colony, so it should not be excessively cleaned.
Since the animals naturally work a lot, it is suggested to give them some task. For example put the food into different chambers, blocking the tubes with potato, giving wood or paper tubes to chew, etc.
In captivity their diet consists of sweet potato, potato, yam (as base diet), and fruits (banana, raisins, peach, apple), vegetables (carrots, peas), corn. They like potatoes too. They are fed with balls made from ProNutro powder in many zoos. Water should never be given to mole rats.
The naked mole rats can be sexed by holding the animals upside down by the base of the tail and looking between the two orifices for the presence or absence of a horizontal red line. The presence of this line indicates a female; unfortunately it cannot be seen clearly at some young specimens.
After birth it is suggested to provide the most possible calm for the animals for about 4 weeks. During this time work with the exhibit should be reduced to changing food only. The animals can control the group number, if it is too high (related to the area), they start to kill and eat the babies, and bring up few of them only. Although they become mature at the age of one, I experienced that they only started to breed at about the age of two or three. Good queens have babies about every 80 days.
The animals should be caught at the base of tail. They usually don’t bite – at least I have not experienced it yet. Never separate an animal from the rest of the group for more than few minutes, unless you want to found a new colony. Having lost their odour they may be attacked by other group members.
For introducing new animals to a colony they should get the odour of the receiving group. The material of the toilet chamber can be used for this purpose. Spending one hour in a separated chamber filled with this material is usually enough. This method is successful when introducing young animals to each other; fighting is short and not very serious – according to the guideline. My experience was not that clear. First we introduced two young females to a male – there were not any problems, only some light fighting, but after 1-2 hours they calmed down. Later they began to breed but after that the subordinate female died. However, in the other case, introducing new males to the queen’s group (three young males to two old females) was much more problematic. After one week and some battles under our supervision the results seemed to be promising, but in the third week a serious war broke out. Finally, the old queen and the largest new male remained in the group and they still have not started to breed for years now.
So, finally, we can answer the question in the title: not as difficult as it is believed. If you are interested in a wonder of the animal kingdom, I suggest you try keeping this species, you will enjoy it very much, and the visitors will, too.
The videos and photos were taken in Szeged Zoo, Hungary