After a very dry wet season, the bush surrounding the Broome Bird Observatory looked brown and dry. The sandy soils of this part of the Kimberley are dominated by Coffee Fruit (Grewia breviflora), Helicopter Trees (Gyrocarpus Americanus) and Broome Pindan Wattles (Acacia eriopoda), with diffused tufts of Spinifex grass in the understory. Although this habitat offers most abundant food in the wet, opportunistic feeders as the Agile Wallaby (Macropus agilis) are perfectly able to broaden their diet by shifting to alternative food resources, such as fruits, leaves and roots from other plants: the tracks that can be found on the beach every morning show those marsupials come to the mangroves to feed on propagules during the night.
But Agile Wallabies are not the only creatures that harvest the beach after dark. Every morning before the sun rises, thousands of Land Hermit Crabs or irramunga (Coenabita variabilis) commute between beach and bush after the collection of their newly found homes. A journey that many are not likely to survive when crossing Crab Creek road – a journey that unfortunately leaves many wallabies lethally injured too.
However, not the hazardous traffic, but the poor nutritional environment in the dry season is the biggest danger, leading to high mortality amongst dependent young. But as pouch occupancy is high year round, the population of Agile Wallabies around the Observatory is still so big they are impossible to miss. Just sitting still in the shadehouse delivers the best opportunities to see them cautiously moving towards the birdbaths for a drink – quickly vanishing again at the slightest sound or movement.
An interesting pairing of animals here. Enjoyed reading the informative details – setting the scene relating habitat, vegetation and inhabitants. One kind of marvels at the evolutionary path of the marsupials and their ability to survive in a harsh environment. ‘Pouch occupancy’ sounds like a protective place before having to face the realities of the big world.
Thanks Liz! Evolution is an astonishing phenomenon, and the way Australian mammals and birds have adapted to the ever drying evironment is truly remarkable. Joeys generally stay in the pouch until they’re able to feed themselves. As soon as the joey leaves, the female will further develop the embryo that is already present, as female kangaroos and wallabies are permanent pregnant – as a joey I wouldn’t be in a hurry 😀
Aha! Now i understand the term ‘pouch occupancy’ :). Thanks Maurice.
You’re more than welcome, Liz 😀
Very interesting to read about the ecosystem. We are having a “dry” wet season too in Florida.
I’m afraid chaos in global climate patterns are changing our natural environment rapidly, Pam, and Australia seems to get hit really hard with unprecedented droughts, coral bleaching and mangrove
die-off. No doubt Florida experiences similar conditions?
Florida is hanging in there, but overall the weather patterns are more extreme than they used to be.
Always interesting to see how animals are adapting to the changing world around them, and mind-boggling the thoughts about where that may take them on the evolutionary path. And as always, lovely photos Maurice!
Thanks! It certainly is mind-boggling, Dries. It’s also so hard to believe marsupials originated in North America, especially now they’re such iconic Australian mammals that have evolved in complete isolation. That’s why I love natural history I think 😀