March 22, 2012

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Spiders in Borneo: Spiders in leaf litter

By Wayne Maddison

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This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American

In my post "Jumping spiders in the forest" I explained how a forest contains hundreds of different habitats for spiders. Now, let's get down on our hands and knees, and crawl around the ground.

In most forests, the ground is covered with dead leaves in varying stages of decay. This "leaf litter" can be quite thick, but in many tropical forests it is only a few layers deep, as the leaves are quickly decomposed and their nutrients recycled back into tree growth. The bacteria and fungi that do the bulk of decomposition are part of a whole food web beneath the dead leaves, with many worms, insects, and mites eating the decomposers and each other. A great place for a spider to live.

Many of the jumping spiders that live in leaf litter hop along the surface, scanning the forest floor like lions gazing across the Serengeti. The best way for us to find these is simply to look, walking slowly through the forest, bent over or crawling. When a group of us are doing this, it looks for all the world like someone has lost a contact lens. A small motion on a dead leaf might catch your eye, or once you're practiced at it, your jumping-spider-search-image might be drawn directly to the tiny dark shape on the ground. You then carefully lower an open vial over the spider before it can hop away.

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Some jumping spiders, however, spend most of their time just out of sight, under the leaves. For those, you have to sift through the litter to find the spider. Some people use special sieves to sift out the spiders, literally, but my favorite method is more hands-on. I quickly scoop up leaf litter onto a white sheet I've laid down, then push aside the dead leaves to see what spiders are scurrying across the sheet, looking to return to their beloved moist ground. Here's a photo of me sifting through litter. Whenever I do this, I see so many other kinds of tiny creatures scurrying that I'm reminded how exquisitely rich is biodiversity:

In our "rehearsal" days around Kuching and then in the first couple of days here at Mulu, we have found three species sifting litter that are small and glossy. We have no clue what genus they belong to, so we call them "tiny shiny black" spiders. We're excited to study them when we get back -- we're pretty sure some of them are new species. (For the salticid geeks: we think they might be astioids. The palpi range from dendryphantine-like to balline-like.):

Previously in this series:

Spiders in Borneo: Introduction

Spiders in Borneo: Undiscovered biodiversity

Spiders in Borneo: The guests of honor: Salticidae

Spiders in Borneo: Team Salticid

Spiders in Borneo: Mulu National Park

Spiders in Borneo: Dreaming about salticid spiders

Spiders in Borneo: Jumping spiders in the forest

Spiders in Borneo: Beating around the bushes

Text and images © W. Maddison, under a Creative Commons Attribution 3.0 license (CC-BY)

Wayne Maddison is a biologist who studies the diversity and evolution of jumping spiders. When he was thirteen years old in Canada, a big jumping spider looked up at him with her big dark eyes, and he's been hooked ever since. Jumping spiders hunt like cats, creeping and pouncing, and the males perform amazing dances to females. His fascination with the many species of jumping spiders led to an interest in their evolutionary relationships, and then to methods for analyzing evolutionary history. He received a PhD from Harvard University. He is now a Professor at the University of British Columbia, and the Scientific Director of the Beaty Biodiversity Museum. He has taken it as his mission to travel to poorly known rainforests to document the many still-unknown species before they are gone, and to study them and preserve them in museums for future generations.

More by Wayne Maddison

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