Here at Windgrove, Peter has created the Gaia Walk – a 1.2 km trail that winds through land and time, each meter representing 500,000 years of evolutionary history. There are markers showing significant events, along with plaques depicting life in that era. His objective is to help walkers of the trail feel time unfolding, to embody the distance that has brought life to the present. If you walk the trail backwards from the present, humans show up almost immediately, after only 3-4 meters. The first mammals are a good distance beyond that, in the Triassic period. Peter’s Forest Bench is a good place to contemplate where we mammals sit in this span of time.
Tasmania offers a unique window into evolutionary time, and what it has meant for mammals and their divergence. When this mammal takes a morning walk down the Gaia trail to the beach, I invariably startle large creatures who thump loudly and then vanish with a quick rustle into the brush.Usually this happens before they are even visible, but face-to-face encounters with wallabies and pademelons (a smaller version of a wallaby) have the same result. The thump is akin to a deer’s warning stomp or snort. With the exception of their hindquarters and tail, wallabies look, act, and eat very much like deer, pruning shrubs into topiary shapes and grazing grasses down to a few millimeters, leaving scat everywhere. Wombats show up at times too, looking like a cross between an overgrown groundhog and a bear cub with a cute koala nose. They dig huge burrows and tunnels that would be the envy of any groundhog, and when they spot you, they scoot away with a funny hopping gait. “A wombat eats, roots, and leaves” is true with or without punctuation. Brush-tailed possums are an abundant nocturnal marsupial, with thick fur and a winsome expression. They are also the scourge of Peter’s gardens, being acrobatic and incredibly persistent, necessitating multiple layers of fencing and baffles to keep them at bay.
I finally managed to see Tasmanian devils, also marsupials, by visiting a sanctuary down the road (the “Unzoo”). It acts as a rehabilitation center for animals afflicted with or at risk of contracting the viral cancer that has caused recent decline in their population. Since they are mostly nocturnal, I have yet to see most of the other marsupials that live here, like bandicoot, betong, potoroo, or quoll. The names alone are intriguing, but I am also fascinated by the evolutionary divergence of marsupials from placental mammals. Here, the only native placental mammals are rodents, bats, and sea mammals. How did North America end up with so many placental mammals but just one marsupial – the opossum? What made it so successful to give birth to tiny, undeveloped young and then nurture them in a pouch, as opposed to keeping them inside and attached to the mother’s body until they have more equipment, yet are still fully dependent on milk and protection? It’s easy for those of us more familiar with the latter mode of child-rearing to consider marsupials a strange and less significant sidetrack of evolution, but it’s hard to argue with their obvious success here.
And then of course there are what seem the ultimate bizarre mammals: the monotremes, the duck-billed platypus and the echidna, which split off the mammal trunk well before marsupials and placental mammals diverged. They produce young in soft-shelled eggs and feed them milk when they hatch by way of specialized mammary tissue. I’m still hoping to see a platypus when we travel north next week, but echidnas live at Windgrove. We’ve come upon these spiny anteaters a few times now, lumbering along poking their long, snorkel-like noses into loose dirt, under sticks, anywhere that their tongues can snag a few insects with sticky saliva. They have poor eyesight but keen hearing, so the click of my camera shutter usually makes them freeze and tuck themselves into a ball of quills. One alarmed echidna scooted over to a patch of tall grass and immediately began digging itself in at the base of the plant. With backwards facing hind feet and strong front claws, it was able to excavate a deep pit in no time, and soon only its prickly back was exposed. I was not tempted to dislodge it. If the quills weren’t deterrent enough, the males also have a venomous claw on each hind leg.
There is another group of mammals – the ones like rabbits and feral cats introduced by humans – that has had a profound and often devastating effect on Australian ecosystems, but I will save discussing them for another time. Meanwhile, even though I know it’s futile, I can’t help hoping that I will round a corner on the trail one day to discover a dog-like marsupial with a striped back and wide jaws devouring a rabbit. It’s been officially extinct for almost a century now, but there are those who believe that the Thylacine, the Tasmanian tiger, still roams in wild places here. Windgrove seems like a perfect spot for it.