Dust to dust …

I was walking my usual beat out in the bush collecting mushrooms and I stopped to look at a dead possum at the base of a beech tree. I had noticed it the last time I was out two weeks ago. Since then its body had collapsed and fur was beginning to come loose. It was just the normal decay process happening as it does – dust to dust.

A dead possum in the forest [photo from Backyard Kiwi (Whangarei Heads Landcare Forum) see note at below]

Death in the forest

Possums, along with rats and stoats, had caused the bird population to crash so it was very quiet. It was likely the possum had been poisoned as part of a control programme for these introduced pests. Standing there looking at its remains I heard a rustling. Looking around I saw nothing. I stood and listened. It was a continuous rustling sound. Looking down I saw movement in the dry leaf litter. Looking harder I saw a line, more of an arc, of maggots moving away from the possum. I assumed that they had eaten all there was to eat and they were seeking a place to pupate. I never did find out whether or not this was normal behaviour for fly maggots.

Possum skulls in the forest [photo from http://www.tourism.net.nz]

Them bones …

This was in the late autumn (late April and early May). I kept an eye on the possum remains as it was quickly reduced to bones and a little fur. Then at the beginning of October, I saw a group of mushrooms, Laccaria, growing amongst the bones. Two weeks later there were even more.

This was way back in 1986 during the first collecting season of my PhD. The place was Paua Ridge in the Orongorongo Valley to the east of Wellington. At the time I didn’t think much about but later I learnt of the work of Naohiko Sagara, from Japan, on ammonia fungi.

Sargara had studied fungi that were associated either decomposing bodies, or animal latrines where large amounts of ammonia or nitrogen compound accumulated. In what I was seeing in the Orongorongo was a fungus, Laccaria, in a mycorrhizal association with a tree, Nothofagus truncata, mopping up the nitrogenous waste products from the decomposition of the possum and transferring that nitrogen back to the tree. Neat huh! Natural selection never ceases to astound me.

Laccaria masoniae fruiting around a sheep skull, central North Island [photo Clive Shirley, at NatureWatchNZ]

Two genera, Hebeloma and Laccaria, seem to have become the main ammonia fungi. But not all species in the genera are ammonia fungi. In Australia, it is Hebeloma aminophilum is the one and is known as the ‘ghoul fungus’. Here in New Zealand, it seems to be Laccaria masoniae as it is frequently found growing around bones. However, it has not been proven by any rigorous study.

Further reading (links/corrected checked 9 April 2024)

Clive Shirley. Laccaria masoniae. Hiddenforest. http://www.hiddenforest.co.nz/fungi/family/hydnangiaceae/laccr01b.htm

Chris Drudge, 2016. Some fungi are into dead bodies and waste piles. Rosin Cerate: quirky quality science. http://www.rosincerate.com/2016/04/some-fungi-are-into-dead-bodies-and.html This can be found on the Wayback Machine at https://web.archive.org/web/20210729001323/http://www.rosincerate.com/2016/04/some-fungi-are-into-dead-bodies-and.html

New Zealand Tourism Guide, 2016. Goodnature self resetting traps.  http://www.tourism.net.nz/community/environmental-sustainability/goodnature.html

Sagara, N. 1995. Association of ectomycorrhizal fungi with decomposed animal wastes in forest habitats: a cleaning symbiosis? Canadian Journal of Botany 73 (supplement 1): s1423-s1433.

Note: The dead possum is from Backyard Kiwi (Whangarei Heads Landcare Forum) a community project to restore kiwi to the Whangarei peninsula. http://test.backyardkiwi.org.nz/  http://test.backyardkiwi.org.nz/category/monthly-updates