Large labor of love for stumpy

Having a baby is a traumatic ordeal. Ask any mother. But imagine having to give birth to a child the size of a seven-year-old.

Couple that with being unable to breathe, eat or even move properly for the latter part of your pregnancy and you enter the incredible world of the stumpy-tailed lizard.

According to research being conducted at James Cook University, stumpy-tailed lizard mothers endure an extremely restrictive and trying pregnancy.

"You can usually tell when a female is pregnant because her abdomen enlarges and organs shift to accommodate the baby. But for the stumpy mother it's a much more cramped affair," said Dr Suzy Munns from JCU's School of Veterinary and Biomedical Sciences.

Dr Munns has spent the past five years studying these resilient creatures along with other reptiles.

Australia's stumpy, the largest of the skink family and closely related to the common blue-tongued lizard, has armoured scales covering its body meaning that when pregnant their abdomen cannot swell.

As the baby grows it occupies an increasingly large portion of the mother's body cavity causing internal organs to compress. How they cope with that compression is the big question.

"These lizards give birth to very large live young - 35 per cent of their weight which is the equivalent of me or you giving birth to a seven-year-old," said Dr Munns.

"It must place an enormous amount of stress on the mother as the baby rests on her lungs and digestive tract. It is unclear what price stumpies pay for carrying such large young."

Dr Munns spent a week in the South Australian desert just after breeding season in hopes of gathering some pregnant stumpies to monitor.

"It was really hard this year. The drought has been so bad down there that there was little vegetation and when the vegetation suffers the stumpies don't have much to eat so the body condition suffers as well," she said.

She came back with a mix of 18 males and females but will not know until they reach full term in March or April how many of the females are pregnant.

"I chose females with the highest probability of being pregnant but I don't know for sure. Pregnancy can be very hard to detect as their scales make X-raying very difficult. It really is a waiting game." Dr Munns has already established that the mother's breathing decreases as gestation progresses. In the field, the lizards also stop exercising and eating towards the end of pregnancy.

"They stop foraging for food, shuttling between sun and shade and may find it increasingly difficult to escape from predators," said Dr Munns. "And where we would be eating for two they totally stop. After they have given birth the mother stumpy is in a very poor condition. They survive time after time but at what cost?"

The lung function and exercise ability of the lizards will be monitored throughout gestation by putting them through a series of cardio-respiratory tests on a treadmill. Lung compliance - how stretchy their lungs are and how much pressure is needed to generate certain lung volume - will also be monitored.

Once the mothers have given birth their performance can be compared to that of the males and non-pregnant females.

"We have a limited understanding of the effects of high gestational loads in the animal world and stumpies, which give birth to one to four large young, provide the perfect model to learn just how the body can adapt to extreme challenges," said Dr Munns.

"We can learn so much from reptiles in general. They have an amazing ability to cope with fluctuating environments. They adapt to varying temperatures, large changes in blood ph levels and have the ability to cope with huge changes in food availability. They can eat every day or stop eating for weeks on end.

"That's why they have been very successful for millions of years and that's why they will still be around when we are long gone. Reptiles are a big evolutionary success story and we can learn a lot from them."


Editor's Note: Original news release can be found here.