Scenting Eggs for Embryonic Training- a quantum leap for reptile breeders
by Jon Coote, Director of Research & Development, T-Rex Products
Herpetoculture, the captive husbandry and reproduction of captive reptiles and amphibians, has advanced mainly by steady evolutionary developments and less commonly by quantum leaps of new ideas and discoveries. Examples of these quantum leaps are our abilities to now accurately determine the sex of reptiles and the fact that varying environmental conditions, particularly of temperature, encourage a successful reproductive response. Our increasing knowledge of nutritional requirements, and especially of the vital requirements for adequate levels of vitamin D3 and calcium, are more evolutionary, and have contributed particularly to the success of lizard husbandry. These evolutionary developments are because our understanding of herpetocultural nutrition can be initially extrapolated from research on other captive vertebrate species.
Perhaps the main sense that reptiles employ in their daily interactions with each other and their environment are their sense of smell. The importance of their sense of smell cannot be under estimated in their function to allow them to identify that which is edible. This can be a problem in herpetoculture which effectively limits the species that we can successfully maintain and reproduce.
Many species have particular food preferences as juveniles which are not shared by the adults. So it may be possible for us to successful keep the adults but then find that it is impossible to get subsequent hatchlings to feed voluntarily. A good example is the African Tiger snake, Telescopus semiannulatus, adults of which has been persuaded to initially take small mice using the new T-Rex Lizard Maker scent, and then transferred to taking unscented small mice without further problem. Captive bred hatchlings have proved to be more intractable to get feeding, although as yet the T-Rex Lizard scent has not been available to use with them.
So if there was a reliable new technique to encourage hatchling reptiles to take foods that are easily available, and equally nutritious and digestible to that which they would normally eat in the wild, it would increase the number of species that could become part of mainstream herpetoculture. It would have to be a technique that could utilise easily available manufactured scents or flavours that are currently available, and preferably those flavours would be of prey species that are normally fed to captive reptiles, such as the range from T-Rex, which, as well as the new Lizard Maker mentioned above, also includes Mouse Maker and Cricket Maker. These flavours are also readily available from the pet trade to subsequent purchasers of hatchlings that had been educated to feed voluntarily using them.
The unpublished work of a PhD student, Helga Sneddon, and other members of a team under the supervision of Professor Peter Hepper, in the School of Psychology, Queen’s University, Belfast, UK, may have established just such a technique during their research into embryonic learning. They have discovered that they can influence the feeding response of hatchling crocodiles by exposing them to manufactured food smells before they hatch. The project was in part designed to help the captive reproduction of endangered crocodilians by encouraging an active feeding response in hatchlings, which frequently are unenthusiastic in their response to available foods.
The decision was made, for research purposes, to experiment with a flavour which would normally be entirely unnatural to a crocodile. For this reason the flavour chosen was strawberry as this could be assumed to be an abhorrent flavour for such a confirmed carnivore as a crocodile. Fruit eating crocodiles are unrecorded, other than where incidental or accidental ingestion has taken place.
The artificial strawberry flavour was painted onto the incubating crocodile eggs for an exposure period of sixteen days prior to hatching. At ten days after hatching the baby crocodiles were offered two dishes of the same food, but with one flavoured with the artificial strawberry flavour. More than six out of ten of the baby crocodiles voluntarily opted for the dish of food flavoured with strawberry. These baby crocodiles had already developed a taste and acceptance for strawberry flavour before they had ever eaten for the first time.
I am not sure how pleased customers of most captive bred carnivorous or insectivorous reptiles would feel about hatchlings that required something as bizarre as artificial strawberry flavour on their food.
Professor Hepper said: “There is a conservation interest with crocodiles in this work. To conserve the species it may well be that, if you can get them to eat more readily after hatching, there is a greater chance of survival. If we can add something to the food that they have been exposed to in the egg we may be able to get them to eat more.”
The same research team has employed this embryonic learning technique to chickens. Exposed to strawberry flavour whilst still in the egg during incubation they went on to show a marked preference for strawberry flavoured food. Professor Hepper hopes that the technique can be useful in pre-determining what foods animals can best be given to eat.
The team also studied similar effects in human babies. Twelve babies were exposed to garlic flavour whilst still foetuses in the womb. Garlic was chosen because it is a sensory stimulus that can cross the placenta and reach the foetus. Babies normally demonstrate marked avoidance of anything flavoured with garlic. Those twelve experimentally exposed to it prior to birth were subsequently far more tolerant of the smell of garlic when exposed to it on a cotton bud.
Professor Hepper’s research team is interested in all aspects of early learning. They aim to investigate all animal groups to see if the same effects of pre-hatch or embryonic learning are present. To date all vertebrate species investigated appear to show the same effect.
The implications of the general adoption of this truly quantum leap technique by herpetoculturalists promises to ease the captive raising of existing, problematic, captive bred species, whilst opening the door to new species previously considered practically impossible to get feeding as hatchlings. Already similar experiments conducted with T-Rex’s Mouse Maker have encouraged an active feeding response on pinkies for the subsequent hatchlings of Corn snakes, from parents that previously routinely produced difficult hatchling feeders. I await the future with interest to see how effective and wide ranging this revolutionary technique will prove to be in successful herpetoculture.
Jon Coote is T-Rex’s Director of Research & Development and is responsible for the introduction of the current T-Rex Products Inc. range of artificial flavours for captive reptiles.
