Saturday, 30 April 2011

New arrival: Pallas' Long-tongued bat

Just gone on show in Twilight World is a group of Pallas’ Long-tongued bats, Glossophaga soricina. These are quite a significant addition to Bristol’s species list, as according to ISIS this makes us the only zoo in the UK, and one of only 10 institutions worldwide, to have them on display.

Bat taxonomy has undergone a lot of revision in recent years, and the old split between the Old World fruit bats (like our Livingstone’s) and all other bats has been abandoned. Instead, bats are still split into two groups, the Yinpterochiroptera, which includes both Old World fruit bats and the horseshoe bats, and the Yangochiroptera, which includes almost all the others. Glossophaga belongs here as a member of the family Phyllostomidae, a New World group of bats found in Central and South America.

Phyllostomid bats are extremely diverse in their ecology, and although many still feed on insects others are predators (the largest of these, the False Vampire Bat, can take birds the size of pigeons), fruit feeders, or like the Long-tongued bat, feed on nectar. The true vampire bats Desmodus also belong in this group. The fruit feeders are important in the distribution of seeds of forest plants, and the nectar feeders are important pollinators.

There are about five species described of Glossophaga bats, but they cover a huge range and it is very possible that there are several cryptic species involved. Because bats identify each other by call, they have no need to develop physical differences to aid species recognition, and any group of bats that are studied so far have revealed numerous species which are almost identical except for their ”call-sign”. This is true even in Europe – only in the last few years was the commonest British bat, the Pipistrelle, realised to be two different species, now called the Soprano and the Common Pipistrelles. Our own species as it stands is found from Argentina north to Mexico

Long-tongued bats have huge energy demands, using up 50% of their stored fat in a day, so they must feed constantly during their activity period to stay alive. They must move constantly from flower to flower, and this of course means they also transfer pollen. As a favourite food source are the flowers of Agave, the source of tequila, it is in the interest of many that they thrive, and as long as their roost sites are safe (these can be anything from a hollow tree to an abandoned mine) they can make use of agricultural landscapes. Aside from nectar, they will also feed on fruit and insects.

As they are found in Costa Rica, where our butterflies come from, they are also important in the ecology of Heliconius butterflies – several important Passiflora species (the foodplant of Heliconius larvae) have white, night-blooming flowers that are pollinated by bats. Examples would be Passiflora mucronata, P.trisecta, and P. penduliflora amongst others. Typical bat-pollinated flowers can be identified as fairly large, usually white, and often strongly scented – these bats seem to use their sense of smell as much as echolocation to find their food, although they presumably echolocate when hunting insects, the other main component of their diet

The societies of different bat species are only just being understood, but it appears that female Long-tongued bats form maternity roosts when raising young and live in mixed-sex colonies the rest of the year. How males compete for females is not yet fully understood – in some other species they perform song flights, sing from perches, or take part in a mass display similar to the leks of some birds. They produce only one baby at a time, as with most bats, and the maximum recorded lifespan is 11 years.

Our bats are housed in a room-sized enclosure in Twilight World, illuminated with green light (which they cannot see). The room is filled with live plants and has the sides decorated with branches to provide perches when not flying. A couple of upside down 30cm plastic flower pots provide a roost area during the day. Feeders are hung round the enclosure so that several can feed at the same time if they wish – the diet is an artificial nectar similar to what is fed to our lorikeets.

It is estimated that perhaps a quarter of all mammal species are bats, and their conservation has in many cases been sadly neglected, as their habits make it very difficult for people to enter their world. Even the small insectivorous bats found in the UK are extremely diverse (17 confirmed breeding species plus some vagrants from mainland Europe), so a good start would be for people to stop using phrases like ‘there’s a bat’ – that is about as meaningful as saying ‘there’s a bird’ when you could be referring to anything from a wren to an eagle. For information on native British bats check out the Bat Conservation Trust website at

(images from the net)

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