Saturday, 27 June 2009

Well done Emma!

There are many things people can do to help gorillas either directly or via gorilla charities. Jumping out of an aircraft at over 10,000 feet wearing a gorilla costume is not one I would choose, but one of the Sunday volunteers I work with has done just that. Emma has just turned 21, and got the skydive as a birthday present from her parents. All I can say is – she has more guts than me by a long shot. One minor problem – the feet came off on the way down, so if anyone finds them could they send them to Bristol Zoo?

Saturday, 20 June 2009

Year of the Gorilla 5: The dark side of gorillas

Gorillas. Peaceful, placid vegetarians, wanting only to be left alone for a photo op with David Attenborough. It is quite impossible that these gentle giants could have a nasty streak.

Yeah. Right.

Actually, all the great apes have a violent streak. Humans of course are the most creative in this respect, but all our close relatives can be killers too. Chimpanzees go in for tribal warfare, orang-utans go for sexual assault and many wild bonobos are missing fingers from fights.

With gorillas, violence takes the form of infanticide. This is not just an occasional accident, but a deliberately pursued policy of attacks on infants, especially by solitary silverbacks, with the goal of persuading females to join new groups.

The rationale behind the attacks seems to go like this:

1. A female with an infant is unlikely to leave the group she is in unless the silverback dies.

2. Silverbacks are hard to kill, especially if they have a group of breeding females to help them.

3. If a female loses an infant, she is likely to abandon the silverback who failed to protect her baby.

4. Even if the male whose group she joins is the one who killed her baby in the first place

Even if a female without a baby joins a new male, if she gives birth soon after joining, there is a good chance that the silverback of the group may kill her baby, despite what are usually vigorous attempts at defence.

This kind of behaviour is widespread in many animals with a reproductive system of a single (or small number) of males and a larger group of females, especially when raising a newborn to independence takes a large part of an adults life. By killing unrelated infants, the male increases the chance of his own offspring being raised before he is replaced in his turn.

So far at least, infanticide has mostly been observed in Mountain gorillas, where infanticide causes about 37% of infant deaths (total deaths in the first year of life run at about 34%). Putting these two numbers together, it suggests that 1 in 10 baby Mountain gorillas are killed by their own kind before they are one year old.

In Western gorillas, infanticide (so far) seems to be less common. This is probably because, as mentioned in a previous post, Western gorillas seem to live in extended clans of related male family groups, and any unattached males are likely to be related to any infants they encounter.

The heavy poaching that Mountain gorillas have experienced has probably made matters worse. Silverbacks are the first to be targeted by poachers, and the result has been a breakdown of gorilla society where unrelated males, fleeing poachers, have moved into areas where they are unknown and any infants are not related to them.

All this has implications for gorilla conservation, especially the release of male orphans into the wild. Release of human-raised or captive bred animals is problematic in any case, because of the risk of exposure of wild animals to human diseases caught in captivity and the difficulty in teaching true independence to an animal which has not had the opportunity to learn how to survive from its mother. Releasing even successfully rehabilitated males into a social environment where they do not know the males in the wild groups they encounter might well do more harm than good, resulting in increased attacks on infants by the new males and a negative impact on the wild numbers.

In future posts, I will discuss how orphaned gorillas are cared for and what can be done to give them at least near-normal lives.
Picture - Salome and Komale, Bristol Zoo gorillas

Saturday, 6 June 2009

Bristol Festival of Nature and other news

This morning I went down to the Bristol Festival Of Nature down by the harbour side. This has been going on for several years now and is basically a shop front for a huge variety of societies and conservation organizations, especially those in the Bristol Area. The zoo was represented of course, both by volunteers looking after some invertebrates, and representatives of the Education department – Bristol majors on education and has at the last I heard over 10,000 pupil visits per year. For full details of the programme – which continues tomorrow – see here:

There are loads of activities for children, and important local groups like the Avon Wildlife Trust and Bristol Naturalists, as well as national groups like the RSPB, The Hawk and Owl Trust, and the Wildfowl and Wetlands Trust.

On other news, as part of the publicity and fund raising for the Year of the Gorilla, one of our Sunday volunteers (the day I work) is doing a sponsored sky dive. All I can say is that she does not look the type to jump out of a plane at 10,000 feet (especially wearing a gorilla costume) If you would like to sponsor her, go here:

I will be posting next week on the Bath & West show, which was a great success - have agood weekend everyone - I have to go paint the hall.

Monday, 1 June 2009

Land of the Dodo 10: The other pigeons

Aside from the Dodo and the Rodrigues Solitaire, there were at least four and possibly five endemic species of pigeon inhabiting the Mascarenes, of which only one, the Mauritius Pink Pigeon (shown at top of post), barely survives. In addition the Madagascar Turtle Dove was present and either survived or was reintroduced from Madagascar.

The main causes of the extinctions were rats, monkeys, and most seriously hunting. Judging from the behaviour of the surviving Pink Pigeons, the birds had practically no anti-predator responses and would not learn caution, or at least were wiped out too quickly to acquire any.

The pigeons can be divided into two genera, the first, Nesoenas with affinities with Africa included the Madagascar Turtle Dove and the Pink Pigeons (two species on Mauritius and Reunion, of which the Mauritius form survives), the second, Alectroenas (Blue Pigeons), with Asian affinities and species on Mauritius, Rodrigues, and probably Reunion. Why the Blue pigeons died out is not altogether clear – Alectroenas pigeons are still widespread on the Comoros Islands and the Seychelles despite human presence. Possibly habitat destruction overwhelmed them too quickly to adapt. The loss of the Mauritius Blue Pigeon, known as the Pigeon Hollandais because its colours resembled the Dutch flag, is a great loss to the islands – a picture of the Seychelles Blue pigeon is shown here:

As well as losses, several species of pigeon have been introduced to the islands – the ubiquitous feral pigeon of course, as well as Spotted Dove and Laughing Dove (both from Africa) and the Zebra Dove of South East Asia. These do not seem to compete directly with Pink Pigeons but they are potential reservoirs of disease.

Today the Pink Pigeon is the subject of intensive effort to rehabilitate the species. Bristol Zoo has bred them in the past, but it has proven extremely difficult to breed outside of Mauritius, and there are currently 49 in European zoos (including four at Bristol), with another 43 in the USA. In the islands breeding and protection of wild nests has boosted the population, and as of December 2008 the wild population stood at 393 birds. This sounds very small, but is a considerable improvement on the situation in 1986, when only 12 birds could be found at the only site they survived in.

Aside from predators, the main threat appears to be habitat degradation. Pink Pigeons are adapted to feed both on the ground at at the end of long branches, and deforestation and introduced plants do not provide the correct food. Fortunately they take readily to bird tables, so supplemental feeding is easy to provide. Indeed, there was an attempt to release birds in one of the botanic gardens on Mauritus. The birds survived, and even bred, but were wiped out by small boys with catapults, for who they made easy targets.

Despite the setback, new populations are being created. Most recently a new sub-population using translocated birds was established at the lower Black River Gorges, and the first fledgling left the nest in September 2008.

As the Reunion Pink Pigeon was closely related to the Mauritius form, which was its ancestor, it might be possible in the future to reintroduce them to Reunion. Unfortunately, at this point politics intervenes. Whereas Mauritius, with Rodrigues, was a British colony and is now independent, Reunion is a French Overseas Department, so there is less connection between conservation on Mauritius and Reunion than there should be.