I’ll never forget going hunting in the mountain ranges between Lewis Pass and the St James, glassing the tops for red deer and chamois, when through the corner of my binoculars I caught a glimpse of a bunch of slow-moving, large animals.
For a moment, I thought I had gotten onto the biggest mob of deer I’d ever seen (hunted wild meat is the only meat I eat, so life depended on it)! Alas, on second glance they certainly didn’t have four legs, they weren’t the right colour and they had extremely long black necks. A flock of Canada geese ambled their way effortlessly up the mountainside through the tall tussocks towards a subalpine tarn (a mountain lake). That was not the only time I’ve noticed this phenomenon. Another unexpected encounter took place when I arrived with my teammates at a Department of Conservation monitoring plot high up in the Raglan Ranges dividing the Marlborough and Nelson regions. At 1700 metres, near the head of a stunning side valley, at least 30 of these large birds stood around in a near-pristine alpine stream.
It appeared the Canada geese had made themselves right at home in this area, littering the place with their distinctive, elongated turds. Immediately I scoured around for weedy species and sure enough, found several exotic herbs that almost certainly had been recently introduced there – perhaps by geese, or perhaps by the three giant red stags that were hiding behind a large boulder on the edge of the adjacent scree slope. I dissected thousands of faecal samples from many animal species as part of my PhD on alpine plant seed dispersal, so I know for certain just how capable both these species are of dispersing intact seeds of native and exotic plant species around the landscape.
Everyone knows that Canada geese have become a huge problem in some areas, especially in agricultural landscapes. They’ve been known to foul waterways due to their large numbers and cause damage to crops. Yet we know little about their impact in alpine systems. One could speculate on some of the unwanted consequences from Canada geese – disturbance, nutrient enrichment and weed dispersal. However, they may also have positive roles to play such as in the dispersal of native plants and in adopting a niche left by extinct native avian grazers.
There are other species that are also spreading their ‘wings’ and venturing high into the big mountains that we underestimate or just don’t understand at all well. Let’s talk about hedgehogs. Nowhere can I find any information to suggest that: (a) hedgehogs hang out in alpine areas, or (b) climb trees, or (c) eat mostly fruits in the peak fruiting season, yet I know all these things are true. Two seasons of counting hedgehog poops informed me that during the height of the fruiting season, hedgehogs preferred fruit over invertebrates (with the odd lizard thrown in for protein), and most of these fruits were Coprosma propinqua. If you know your Coprosma, you’ll know that C. propinqua come in the form of reasonably tall shrubs with a decent stem and are often a good 1-2 m tall.
Not too many of their fruits litter the ground below the canopy – certainly nowhere near enough for hedgehogs to have sought them out to eat (and then pass as hundreds of seeds in their poops). The only feasible answer, of course, is that hedgehogs climb trees! I do realise I need to back this up with some video evidence for my theory to be accepted by the masses, so I am planning some hedgehog tree climbing trials and will use my infrared camera to capture this. I have also recorded hedgehog poops right up above treeline too, so they most certainly seem to be making the mountains their home now.
Another underestimated mammal in the alpine zone is the large gentle-looking creature we occasionally frighten out from behind a tussock – the European hare. They look so cute and innocent, incapable of causing damage because we usually only see one or two at a time if we are lucky. We often don’t even see them at all and only know they are there from their pellets. They run for their life when we disturb them and we never get to see what they’re actually eating!
They’ve been around a long time but have never really been the subject of dedicated, widespread control. It seems to me that in alpine areas, hares have already eaten out some of the most palatable plant species to low numbers and the structure and composition of some alpine communities today is perhaps by no means an indication of what they were like before hares arrived. It is very difficult to tease apart the impacts of hares relative to alpine-dwelling ungulates or possums, so this warrants further study (if you’re willing to build some snow-proof exclusion fences and check them every year)! There is massive scope for better understanding the ecological impacts of hares as there is really only one decent study on their diet (by John Flux in the Nelson Lakes area).
And what business is it of pigs to enter our high mountain areas and dig them up! See the photo below showing before and after pig damage high in the Tasman Wilderness Area of Kahurangi National Park. Similar damage is evident elsewhere. For example, when flying over tussock grasslands in the Hawkdun Range or through the Molesworth, pigs can be seen scattering under the chopper with large areas rooted by these ecosystem engineers (of the worst kind).
Animals are of course constantly on the move, invading into places they haven’t been before – the nature of most creatures on earth. But while we as conservationists are trying to limit or reverse this movement, we are often competing with the ever-increasing pressure of hunters moving different species of deer, as well as pigs, around the landscape.
It’s not just mountain systems that we should think about but it is a good example and representation of a potentially much wider issue. What about those roosters that people dump on roadsides, simply because they’re not wanted in the household chicken coop? Are they staying put on those road verges, rarely venturing into the bush, or are they becoming more adventurous and exploring further afield? Should we be on the lookout for feral bush chooks and asking questions about what impacts they are having on our native ecosystems, especially on invertebrates?
Geese, hedgehogs, hares and pigs are just a few examples of the animals we know are out there but aren’t considered serious pests in mountain ecosystems. It is not a new or difficult concept, but perhaps it is time for us to take a closer look and ask ourselves what we think the new “possums, stoats and rats” might be in say 50 years time. Which of these already-present animals have been simply lying “dormant” and waiting for their time to come to invade into and adapt to susceptible mountain ecosystems? Should we be watching more carefully for our next serious animal pests just as we do for new weeds? It may well be to our peril if we ignore them.
A version of this post originally appeared in the New Zealand Journal of Ecology’s newsletter.
Featured image: Flickr CC, Richard Carter.