Eyes carefully scanning the leaf litter as they pick their way gingerly through dense forest, the small group of students engaged in primate research are keenly alert to possible dangers in the undergrowth. Already disorientated from having taken a couple of steps off the path to pop to the loo, the major risk they now face is becoming even more lost by straying further into the forest.
Another danger could be venomous reptiles ... but those are rare, to be honest, here in Little Wittenden Wood in deepest Oxfordshire. But what's that hanging there, from that overhanging branch? Is it a copperhead, a cobra or a mamba? Or is it a lurid yellow plastic snake from Toys R Us?
A good few of the students have missed it, which, given the lack of camouflage afforded by the leafless branches, seems hard to believe. But that's the lesson of this practical exercise in jungle survival: even when you're primed to look carefully, spotting the dangers that lurk behind each tree stump is a hard skill to master.
The 20-odd Oxford Brookes postgraduate students who are gamely practising survival techniques on a chilly English afternoon will soon be heading off on the fieldwork element of their primate conservation MSc. Given that many will be living and working in remote rainforest, usually with limited road access, basic communication equipment and few, if any, medical facilities close by, learning ways to prevent a crisis - by, for example, ensuring you don't slice into your shin while swishing a machete to clear a route - could literally save your life.
Across the clearing, there's a sudden sharp ring of steel on wood and a shower of splinters flies through the air. Two of the students laugh nervously and duck for cover, as with a few deft sweeps of his machete, Haja Rambeloarivony neatly splits in two a fallen oak branch. He demonstrates perfect technique: his left leg pulled well back for safety and the machete slicing precisely downward into the wood.
"How old were you when you first used one of these?" asks Nigel Hodgson from the expedition and wilderness company Fieldskills, which is leading this three-day course. "In my teens when I used it for real in the forest, but when I was a little boy - maybe five, six, seven - I would play with one to get accustomed to it," grins Rambeloarivony.
Coming from Madagascar, Rambeloarivony is clearly rather more familiar with jungle environments and the skills needed to inhabit them safely than most of his fellow students. Being able to navigate with a compass is pretty crucial to rainforest fieldwork, too, though as Fieldskills makes clear, getting good at it requires sustained practice in a variety of terrains.
"Every year you hear of colleagues being lost while engaged in field research, and quite a few people disappear altogether," says Professor Simon Bearder, who directs the MSc. "We've been very lucky since the course started and haven't lost anyone yet. But you can't rest on your laurels. One student who got trapped on an island after the tide came in was very badly sunburned. This training is intended to help them think about how to plan ahead."
As part of a global research team specialising in nocturnal primates, Bearder - who says he learned many of his field skills as a boy scout - is often to be found tramping through jungles across the world in the pitch black of night beneath a forest canopy blocking any moonlight that might otherwise help him see his way.
"Tracking nocturnal animals certainly sharpens up how observant you are," he says. "But of course, there are no paths where you're going and you can easily get lost. It happened to me once following a bush baby in Ofkolaco, South Africa, where I'd been working for two years, so I was very familiar with the territory. And it's horrible. You just have to sit down, try to calm yourself so the fear recedes a little, and think logically. I heard water running, so followed the stream down."
Oxford Brookes isn't alone in its concern about the dangers some research students may face. Leeds, Edinburgh, Glasgow and Oxford universities have all recently commissioned survival skills courses.
Where Ray Mears and Bear Grylls lead, would-be adventurers seem keen to follow, no matter how cold, hot, wet, dry or miserable the experience in store. Fieldskills has recently expanded its UK operations and is offering new courses and training expeditions here and from its Borneo HQ; its clients include school and university students, expedition members, and intrepid travellers keen not to find themselves dying of hunger, thirst or a snake bite.
Given that geographers, archaeologists and biologists, for example, are likely to carry out fieldwork in conditions ranging from the arid plains of Africa to the freezing wastes of the Antarctic, getting students prepared is increasingly seen as a wise precaution - even if realistic conditions cannot always be mocked up in harmless Oxfordshire.
This particular course on jungle environments includes basic first aid and fieldwork safety; avoiding, recognising and managing heat-related illness; tropical hygiene, expedition logistics, how to deal with big scary animals - and also with smaller, but possibly even deadlier ones - as well as techniques for crossing a river safely and, very usefully, how to avoid being killed by a dead tree.
Pre-expedition planning is the Fieldskills mantra. The idea is not to have to survive days of wandering round in circles (fairly inevitable, apparently, without access to a compass), licking raindrops off leaves (dodgy, as water is no longer pure once it's trickled through the canopy) and grubbing around for edible insects for your dinner (vile-tasting as well as dangerous). Tucking up in a safe, dry bed at your safe, dry HQ after a working day spent tracking your primate is the name of the game.
So, having learned where to site a latrine and how to spot a plastic snake at five paces, how do these students now rate their survival chances?
"I think the fact that you've thought about how to manage things before they happen would help you not to panic," says Kate Moise, who will soon fly to Borneo to study juvenile gibbons.
"They've even talked about practical stuff you'd never think of, like your insurance, and how good it is," says Lara Rogers, who will be researching the Bengal slow loris four days' trek into the Cambodian jungle. "You know, would they evacuate you in an emergency, or are you going to have to hang around for weeks with a broken ankle? My mother has already been on the phone to check it out."
As per the training, her fellow student and research colleague, Camille Coudrat, has been pondering the possible risks in the areas where they'll be working, such as landmines.
It won't stop them going; the research station they'll be based at is well established and well run. And, in any case, as their tutors are keen to emphasise, this training is not about expunging all risk; it's about understanding what they may come up against so they can crack on with the planning that prevents an accident from turning into crisis.