National Zoo
National Zoo Twitter Facebook
Please donate!
National Zoo Home Previous issues NZG website Contact us

September 2014
Contents / home
Getting up close to DNA
Environmental education goes international
Feral goats display unique genes
Welcome to our new penguin chicks
Biobanking ties strengthened
Clever and brave salamanders
Heritage Day celebrated in awesome style
It’s a mere 101mm and as cute as a button
Conservation Grapevine

Axolotls display aptitude for different feeding methods

  The PVC piping, with both ends open, was found to be the best feeding option
  The creatures found it difficult to back out of the transparent tube with only one open end
  Getting in and out of the transparent plastic container with the holes in was easier for the axolotls to get in and out of
The axolotl (Ambystoma mexicanum) is a comical-looking creature and although it is colloquially known as a "walking fish", it is, in fact, an amphibian.

The National Zoological Gardens of South Africa (NZG) currently houses a group of 18 axolotls of which nine are juveniles. The youngsters were reared by conservation staff at the Aquarium to give them the best in life.

Listed as critically endangered by the IUCN’s red List of Threatened Species, the axolotl is historically found in Lakes Chalco and Xochimilco of the valley of Mexico near Mexico City. Axolotls reached this conservation status in their native habitat largely due to the introduction of predatory fish and habitat loss. These amphibians were the top predator in their native environment making them important in structuring community dynamics.

Axolotls are an important research animal and have been used in studies of the regulation of gene expression, embryology, neurobiology, and regeneration.

In order for the axolotls to thrive they require low temperatures in their tank - below 19˚C. After the eggs had been laid they were transferred to the aquarium’s quarantine area where they were given special care until they hatched. Extra care was further given to the newly-hatched young as they required special feeding strategies, water quality monitoring and good tank maintenance. Due to their cannibalistic nature it was very important to ensure adequate food supply and separating the babies according to their different sizes. This ensures that the smaller ones don’t end up as the bigger one’s dinner!

The young axolotls were fed brine shrimp until they were big enough to be introduced to other food like daphnia and bloodworms. Adult axolotls are fed hake, ox heart, sardines, fish pellets, earthworms, crickets and mealworms.

The gravel layer at the bottom of the tank is very important in supporting bacterial life. However, one challenge NZG staff faced is that axolotls can sometimes swallow the gravel during feeding. For this reason a study was conducted in order to evaluate different and effective feeding methodologies for the adult axolotls kept at the NZG’s aquarium.

The objective was to prevent the consumption of sand in the tank during feeding. This was done to provide the axolotl with sensory and motor stimulation through structures and resources that facilitate the expression of species-typical behaviors. It also assisted in promoting their psychological well-being through physical exercise, manipulative activities, and cognitive challenges according to species-specific characteristics.

Different feeding methods and tools such as a PVC pipe, a transparent plastic tube with one open end, a transparent plastic bowl with a lid, transparent square plastic containers with holes, and a flat plastic lid were used. The food items used in the experiment were hake, sardines, trout pellets, bloodworm, crickets and mealworm.

All food items were cut up into appropriate sizes for the axolotls to feed on. A public display tank housing six axolotls was used for this. The PVC piping proved to be the most successful method used since there was no consumption of sand and the Axolotls were able to move in and out of the pipe. The transparent plastic tube with one open end proved to be least successful since the axolotls could not back out of the pipe once they were in it. The transparent plastic bowl with a lid also proved to be inefficient as it floated. Axolotls are less inclined to take floating food than sinking food. The transparent square plastic container with holes was a success as the axolotls were able to get in to eat and out. However, this feeding method took longer for the axolotls to master as they had to figure out how to get into the bowl.

These feeding experiments proved to be successful in preventing the axolotls from consuming sand during feeding and it also encouraged activity stimulating complex behavior.

Axolotls exhibit a measurable amount of intelligence. They are very curious, relatively brave and can easily be taught different feeding behaviour through environmental enrichment techniques. The axolotls are fascinating creatures that always capture the visitors’ interest and if it happens that you get to experience their feeding then you will surely be intrigued!

By: Thobeka Runganga, Conservator, Aquarium

Zoo and Aquarium Visitor