Royal Society

The Lady's Choice

Only if we understand can we care.

That sentence is the beginning of a quote from beloved conservationist Jane Goodall. It is also the beginning of an idea, growing amongst people in science; an idea that leads biologists away from the forests and deserts of their research and into lecture theatres and radio studios. Our own understanding is not enough. Our own knowledge, sifted and harvested from thousands of hours’ worth of data and records and testing, can no longer rest amongst just those who share in our pursuits. It is the public who matter.

Twice a month, the Royal Society of Victoria takes aim at just this idea with free, open lectures. Ranging through a banquet of scientific disciplines, speakers are chosen to bring information about their work to anyone interested. For those who attended in late February the topic was the encroaching extinction of Victoria’s most vulnerable animals, brought by Dr Marissa Parrott of Zoos Victoria.

When an animal becomes vulnerable, through predation or habitat loss or any other unfortunate cause, the challenge for conservationists is maintaining enough genetic diversity to ensure future recovery. Many times over, isolated populations have shown that an increase in inbreeding leads to a decrease in health. A population of one male and one female will often struggle to survive, no matter how fertile they are.

Socially, the aversion to incestuous relationships is deeply ingrained in a number of societies. From a biological viewpoint this is highly beneficial, for two important reasons. Firstly, inherited disadvantages are much more prevalent in inbred populations – if both parents are hiding some faulty gene received from a common ancestor, then the chance of their offspring receiving two bad copies and no good ones becomes very real.

The helmeted honeyeater. Image: Trent Browning / Zoos Victoria

The helmeted honeyeater. Image: Trent Browning / Zoos Victoria

Secondly, even if all genetic information is functioning normally, the lack of variety means that the species won’t be as capable of coping with surprises. This may be the ability to adapt to changes in the environment, such as temperature and water availability, but immunity is also a major concern. The major histocompatibility complex (MHC) protects mammals from infection by anticipating what bacteria or viruses might look like, building from a combination of variable genes. A greater variety in these genes means a greater number of threats that a species is prepared for, while a limited gene pool is less likely to be ready for rare and new pathogens. It’s like a game of poker with half the deck missing; if there are no aces in the pile, there’s no chance of playing a royal flush when you need to.

Historically, this has made captive breeding programs a very mathematical process. Introducing genetically dissimilar individuals ensures that offspring are biologically equipped with the best chance they could have, and zoos have developed extensive stud books to keep track of family trees. However, developing the acquaintance between the male and female often takes time; slow breeding and small brood sizes were once seen as common.

The agile antechinus ( Antechinus agilis ). Image: John Gould

The agile antechinus (Antechinus agilis). Image: John Gould

Dr Parrott’s work with dunnarts, Antechinus and other marsupial species introduced a different method. She showed that when a female was able to select her own partner, it took less time for the pair to begin reproducing, gave rise to a greater number of pregnancies, and all with decreased aggression between the female and the male. On the surface, this seems like an easy and more certain way of increasing the success of breeding programs. However, the limited resources of conservation strategies mean that every angle needs to be considered and every variable controlled to best create genetically fit and well-adjusted populations. If the female was allowed to choose her own mate from a group of genetically suitable suitors provided by zoo staff, what was the risk of her choosing a bad match?

The dilemma was a strong one. It’s been shown that mammals are more comfortable socialising with individuals they’ve met before, and particularly with family. Dr Parrott and her collaborators’ work with Tasmanian devils at Healesville Sanctuary showed that introducing young devils to one another – growing used to the smells, sounds, and personalities of new animals – led to greater interactions, more activity and increased denning with their conspecifics. While socialising young devils appears to produce more socially competent animals as adults, further research showed that their interest in novel or familiar animals was similar; a good outcome for breeding programs that introduce a variety of potential mates. However, could some females be selecting males that appear familiar, and risk all the complications of inbreeding?

No, it turns out. Not at all. In her 2015 paper, Dr Parrott shows that female Antechinus were perfectly capable of distinguishing between related and unrelated males, and acting accordingly. Her earlier research on the species shows that it largely comes down to scent – among other cues, with a possibility that the MHC produces chemical traces that change how a male smells to a female. Multiple tests showed that females are more interested in those who smell different to themselves, making more frequent and longer visits to males that were genetically dissimilar. Males that were genetically dissimilar to females secured more matings and sired the highest proportion of young. While it’s not yet clear which range of specific cues other than genetic dissimilarity are providing the information, the result is inarguable – the lady knows best. In a system where multiple matings almost always produce a litter with more than one father, offspring were found to have come from genetically distant males around 9 out of 10 times.

With the limited resources available to conservation programs, understanding how to best produce a robust population is crucial. Zoos Victoria’s Fighting Extinction plan has committed to a magnificent goal: that no Victorian terrestrial vertebrates will go extinct on their watch. Ever. This includes 20 high priority species, as well as a watchlist of other vulnerable animals. But the programs aren’t just about breeding and habitat monitoring – we come into them as well, in the small changes we can make to our daily lives. The fantastic Wipe for Wildlife campaign is one such example, calling for the simple change to recycled toilet paper - with its very own superhero. And there’s the Love Your Locals campaign – helping children and adults alike to discover who they’re sharing Victoria with, before we’re left alone.

Only if we understand can we care.
Only if we care will we help.
Only if we help shall they be saved.
— Jane Goodall

Paul Jones

Paul works in science education and has been a teaching member of Monash University's Department of Biology since 2010. He is interested in community engagement and sustainable urban development.