Winter Talk Summaries 2016/7
Mammals of the Galapagos Islands
Jen Jones and Claire Simms, Galapagos Conservation Trust, 14th November 2016
Wildlife on the Galapagos Islands usually conjures up images of exotic reptiles and birds – pre-historic giant tortoises, swarms of marine iguanas clinging to wave-swept rocks, Darwin’s finches or comical blue-footed boobies. However, as we learned at the Oxfordshire Mammal Group Lecture on 14th November, mammals are also important on these islands. Following a brief introduction to the geology and geography, Jen Jones and Claire Simms, of the Galapagos Conservation Trust, gave us a beautifully illustrated and informative talk covering many aspects of wildlife and conservation, but focussing particularly on mammals.
Due to their isolation – almost 1000 km from mainland Ecuador – there are few endemic terrestrial mammals on this cluster of volcanic islands: only 4 species of Rice Rat and two bats. There were previously seven species of Rice Rat, however mainly as a result of direct competition from the larger, alien, Black Rat, three species became extinct. Those that remain have only been found on three uninhabited islands: Santa Fe, Santiago and Fernandina, and very little is known about their ecology. The Hoary Bat and Galapagos Red Bat are both found in highland and coastal locations. Knowledge is limited about their distribution and ecology, however it is likely that they too have been affected by invasive species.
There are two species of marine mammals – the Galapagos sea lion and Galapagos fur seal, and although the latter were once hunted almost to extinction for their fur, numbers of both these species are better documented, although both are considered ‘vulnerable’. Threats include direct attack and disease transmission by domestic and feral dogs, boat strikes and environmental hazards such as devastation to the marine food chain by intermittent oceanic El Nino currents, and more general effects of climate change.
The main topic of mammal discussion on the Galapagos Islands, however, is really to do with the significant and negative impacts of introduced and invasive domestic animals such as goats, cats and dogs, many of which have become feral and destroyed much of the habitat and competed with endemic wildlife. The impact of human settlers and visitors was also discussed – not only introducing domestic animals, but also the unintentional introduction of alien invertebrates and plants which have been responsible for infection and competition of indigenous species. Perhaps the most familiar and tragic tale is that of the almost total annihilation of the giant tortoise by early seafarers, who just saw these wonderful reptiles as a ready source of meat – easily captured and stored.
The Galapagos Conservation Trust works tirelessly with other organisations to protect, conserve and educate local people and those around the world about the critical issues affecting this precious and unique World Heritage Centre site.
For more information please visit their website: galapagosconservation.org.uk
American mink – evil or interesting?
Dr Joanna Bagniewska, University of Reading, 9th January 2017
A show of hands early on in Joanna’s excellent lecture on 9th January suggested that most people see this alien species as an enemy. However, as Joanna reminded us, the American mink (Neovison vison) did not ask to come to the UK – it just happens to have adapted extremely well, and sadly this has often been to the detriment of native species, including waster voles and ground-nesting birds. Introduced from their native North America to supply the fur-farming industry, some animals inevitably escaped, and they are now widespread in Europe, South America and Asia. Carnivores tend to be successful as invasive species, and with a very generalist diet – from beetles to rabbits – the American mink has little trouble finding food. Being semi-aquatic has also increased their ability to adapt, and it was this characteristic which Joanna investigated for her PhD.
Studying diving animals is difficult. Until recently it was only really possible to observe their terrestrial behaviour and extrapolate under-water activity from this. Development of time-depth recorders in the 1960s made the study large marine animals possible, but it is only with the recent evolution of miniscule devices, weighing as little as 1 gram, that smaller animals such as mink can be studied. Joanna made 20 recordings from 16 animals on the Thames and Cherwell Rivers, and studied behaviour during summer, autumn and winter. Diving patterns were very variable – both between and within individuals. Dive number ranged from 1-189 a day, and from under a minute to more than half an hour. Maximum depth was 2.86m. Although there is some ‘niche partitioning’ between the larger males (around 1.3 kg) and females (0.7 kg), there was no significant gender difference in dive behaviour, although females dived more frequently in winter and on balance smaller animals dived more often. Diving occurred all year, with 83% during daylight, and occurred both in clusters and as single dives. This diurnal pattern may avoid competition with the larger otter, which tends to hunt by night. Despite having limited physiological adaptation for diving – high surface area, little insulating fat, poor propulsion under water and non-webbed paws, American mink seem to have adapted well to an aquatic niche.
Whether to protect endangered species or control aliens, it is essential to understand their behaviour and ecology. Working in a challenging environment and using novel technology, Joanna’s research added valuable insight into the aquatic life of the American mink, and while many still wish to remove them, it is hard not to admire the way this feisty little mammal has worked to optimise its survival in the UK.
Photographing Polar Bears
Ross Mackenzie, 5th December 2016
A maze of dark water channels separates islands of glistening ice. In the far distance you can just make out the shape of a large, white-yellow creature standing motionless: this, as Ross Mackenzie told us in his fascinating lecture to the Oxfordshire Mammal Group on Monday 5th December, is how you often experience your first sighting of a polar bear. Keen to emphasise that he is neither zoologist nor ecologist, but a photographer, Ross nonetheless presented us with a lot of useful facts and figures about this iconic mammal. There are nineteen distinct populations, whose distribution was clearly demonstrated on a circumferential map of the North Pole, and a total of around 25,000 bears. Some populations are shrinking, none are expanding, and their conservation status is ‘vulnerable’.
A mother and cub balance precariously on the spine of a dead whale as they feed from its rotting carcass – but in the next shot the sleek head of the cub, looking rather shocked, bobs up from the icy water revealing the harsh nature of this environment. Adults have fat and fur designed to withstand long submersion, but cubs are less well prepared. On dry land, however they frolic and play, or stand and stare with baleful curiosity at their human admirers. The clarity and intimacy of Ross’s photos make you feel you could reach out and touch! However he assured us that these were taken from a safe distance of about 40 metres, and usually from a small boat. Polar bears are curious: once they see you, you can usually sit still and they will approach. But as opportunistic carnivores, they see humans as potential prey. Seals are their preferred diet but polar bears will eat anything, and in urban areas foraging can lead to conflict, with bears sometimes being shot, or perhaps at best – for repeat offenders – taken captive and offered to wildlife parks. We learned of Franklin’s early and fateful exploration of the North West Passage – captured in a muted photo of three simple crosses, recently discovered as the ice retreats.
Predictably, human activity seems to be the main threat to polar bears, with hunger and starvation resulting from habitat loss and alteration. To hunt for seals, they need ample areas of new sea ice, usually at a peak in March – ice of several years old is too thick. Arctic temperatures are rising, resulting in less and later sea ice formation. This year the freeze is late, with temperatures in Svalbard 15 degrees higher than expected: the ice is forming slowly and the outlook for polar bears and their new cubs in the spring of 2017 is grim. We must do our best to prevent escalating climate change, and just hope that it is not too late for these majestic apex predators of the north.
Roger Trout, 13 February 2017
Summary coming soon.