Australian veterinarians, nurses and wildlife carers are adept at hand-rearing orphaned native mammals. Various species of possum, wallaby, kangaroo, bat and glider have been successfully reared and released into thewild.
Any carer will tell you that once the novelty wears off, hand rearing is hard work. Often requiring feeds spaced one to two hours apart, their tiny charges require plenty of dedication and sleep deprivation.
But as Top End veterinary nurses Caroline Francis and Tess Cooper discovered, that’s not quite the case when it comes to raising an orphaned short-beaked echidna (Tachyglossus aculeatus).
The echidna in question, nicknamed Makka Pakka after a character from the ABC’s In the Night Garden, was found in the pouch of his injured mother who was rushed to the Ark Animal Hospital in Palmerston, just out of Darwin. Initially Makka’s mother received veterinary care, but it became clear that she was not responding.
“She had suffered from trauma including major injuries to her digging toes and her condition was deteriorating,” Francis said. “She was losing weight drastically and she reached a stage where she just unfolded her pouch and wouldn’t or couldn’t let him back in.”
Makka’s mother was euthanased, but at around 160grams Makka was far too young to survive without intervention. Weaning weight for echidnas is around 800 to 1300grams – so Makka had a long way to go.
According to published literature, juvenile echidnas or puggles have been successfully hand reared from less than 40 days of age and 150grams body weight. This stage is recognised by the presence of stubble or spines.
“We could just see his spines under his skin,” Cooper said. “We couldn’t feel them all, he was podgy and pretty much pink all over – just a little ball of fat.”
Cooper and Francis took charge of Makka’s care.
The biggest challenge in hand-rearing an echidna is providing a diet that is as close to natural echidna milk as possible. Echidna milk is highly concentrated, high in fat and iron, but low in protein, carbohydrate and lactose. The nursing team chose Wombaroo Echidna Milk Replacer (Wombaroo Food Products). This comes in two varieties: the first is for puggles under 30 days old with less than 210grams, the second for those over 30 days and with a body weight of more than 360grams.
Female echidnas don’t feed their young via nipples. Rather, milk is secreted from mammary tissue through pores in the skin in an area known as the milk patch. Feeding may take two to four hours. In the wild, the mother leaves the puggle in the burrow while she forages for food.
Unlike mammals who require regular feeds to meet their energy requirements, puggles may initially feed once every five to ten days – usually when mum returns from foraging. During these feeds, the puggle ingests around 20 per cent of its body weight in milk, although Cooper knows of one instance in which a puggle guzzled more than double that amount.
And unlike their mammalian counterparts, puggles are highly prone to heat stress. Adult echidnas have a staggeringly low core body temperature (around 32 degrees Celsius) and a metabolic rate of around 30% of an equivalent sized dog or cat. Thus they require a lower ambient temperature in captivity, although if it drops too low they can enter torpor, leading to reduced food intake, inadequate digestion, malnutrition and immunosuppression. According to the literature, they are thus best maintained between 20 and 25 degrees Celsius.
Makka’s feeding sessions, although infrequent, take time. Because the puggle won’t accept a teat, carers have to syringe a small amount of milk onto the palm of their hand, simulating secretion from the mother’s milk patch. In response, the puggle rubs its beak on the hand of the feeder, an action used to stimulate more milk secretion.
Makka’s appetite is variable. Some days the puggle will slurp down 30ml of milk without hesitation, other days only 5ml. On several occasions the carers have administered milk by a stomach tube to ensure adequate milk is ingested. Stomach tubing is a delicate operation as the soft beak can be injured in the process and there is the ever-present risk of aspiration.
“When he had eaten more than 20 per cent in a feed he tended to be less interested at the next feed,” Francis said.
At one stage Makka developed a mild case of diarrhoea but responded well to injections of amoxicillin-clavulanic acid. In addition the milk was replaced by a small feed of Lectade to provide hydration but avoid over-filling him.
“He was weak and wrinkled and struggling to propel himself forward – just not behaving the same way – but he perked up after that,” Francis said.
“Apparently as they get older they become really good at licking food out of a bowl,” Francis said. “At the moment he tends to really burrow his beak into the milk and occasionally blows a bubble out of his nostrils but that hasn’t caused any problems.”
Francis labels Makka a “he” tentatively. Initially his carers had spotted what they thought was a rudimentary pouch on Makka’s abdomen.
“Everyone assumed it was a female because he had that pouch but apparently both males and females can contort their muscles in such a way to make a pouch – so at this stage we aren’t sure what sex Makka is,” Francis said. “That was certainly a surprise.”
Sexing echidnas can be difficult as the proper female pouch is only present in adult echidnas when they are breeding. The penis may be palpated and even extruded, but this is done under general anaesthesia and subject to false negative results. Mature adult males have large hind-limb spurs, although small spurs have been found on some females, potentially confusing the issue. For the sake of convenience, Makka is therefore referred to as a male.
Raising Makka has been a trial-and-error process. While he gained weight initially on every-second-day feeds he went through a period where he didn’t do so well, failing to gain weight despite being fed around 20 per cent of his body weight every other day. His carers altered the amount and frequency of feeds without much improvement initially.
“In the initial stages we really were in unchartered territory,” Francis said. “We sought advice from a number of carers and people who had raised puggles including the Territory Wildlife Park. We didn’t want to over-feed him but we had to make sure he was getting enough energy as during some of those early feeds he was so tired.”
Francis took Makka home over the Christmas period, which is when he really began to drink.
In terms of housing, Makka is kept in an aerated esky in an air-conditioned room with a shredded-paper substrate.
“Some carers have made burrows with dirt but we weren’t really comfortable doing that because of the risk of melioidosis from the soil up here,” Francis said. “Instead we’ve provided a towel as a base and plenty of shredded paper so he can burrow. The paper also provides insulation. Around 23 or 24 degrees seems about the right temperature for him.”
While other mammals require the obligatory post-feed bottom wipe to stimulate defaecation, Makka is quite happy to toilet himself, defecating in an area well away from his burrow.
Makka is currently gaining weight, albeit gram-by-gram, and his or her spines are slowly growing longer. Compared with other patients he is pretty silent, except for the slurpy sounds he makes when feeding.
Once he reaches weaning weight the carers will introduce solid foods including ants, termites and other insects.
“It’s been a privilege to raise him, really, it’s something special for us,” Cooper said. “It has been a pretty intense time because we’re always worried about getting it right. Echidnas are not an animal we see so often in the Territory because they tend to hide out in the Arnhem escarpment.”
“It’s been a bit unusual having to keep something cool all of the time and the huge spacing between feeds, especially when you’re used to hand-rearing mammals. Its often tempting to wake him between feeds to check that he is alright, but we try to let him sleep as much as we can. There’s a lot we don’t know about what goes on in those little burrows.”
Reference
Middleton D (2008) Echidna. In Medicine of Australian Mammals, L Vogelnest & R Woods (eds) CSIRO Publishing pp77-102.
ANNE FAWCETT