The preferred prey of the Natterer’s bat (Myotis nattereri) are flies (Diptera) of the suborder Brachycera, or diurnal flies. Bats hunt at night, and those that are insectivorous or carnivorous must rely on their sense of echolocation in order to find their prey. The difficulty lies in that flies sitting on a substrate such as a leaf or a wall are almost impossible to detect using echolocation. How it is that the Natterer’s bat manages to locate its prey was investigated by studying bats hunting houseflies (Musca domestica) in the setting of a cowshed. The bats seemed unable to locate individual flies sitting on the ceiling, even if the flies were on the move. But interestingly, the chance of being attacked by a bat increased hugely once flies began mating. During copulation, the male fly buzzes its wings, producing click-like noises. The bats appear to ‘eavesdrop’ on these sounds and use them to locate their prey. There is an extra bonus for the bat in listening out for this behaviour - in locating a copulating pair, they get a meal of not one, but two flies in a single attack. Confirmation that the bats were responding to acoustic signals from copulation was given when speakers were installed in the cowshed that played these sounds, resulting in attempted attacks and investigation by the Natterer’s bats. In contrast, they did not respond to lower frequency tones typical of a moving fly, suggesting that they attend specifically to the sounds of flies in copulation. Though this was tested in a cowshed setting, it is likely that this method is also used by bats when searching for their prey in vegetation and other settings.
Ref: Siemers M. B. et al. (2012) Bats eavesdrop on the sound of copulating flies. Current Biology 22(14) [link]
All good men know that the way to a woman’s heart is through her stomach, and none more so than the swordtail characin (Corynopoma riisei). Males of this popular tropical aquarium fish take a rather literal approach to getting the girls “eating out of the palm of their hand” by luring them in with an anatomical ornament that looks like their favourite snack. The exact shape varies with diet across different populations - some, for example, take the form of ants where these are the dominant prey. This is an example of what is known as sensory drive, where sensory communication methods evolve by adapting to local environmental conditions. This can lead to speciation - the division of populations to form new species - particularly in cases like this where mate choice is affected. The swordtail characin is one of the few fish that reproduces by internal fertilisation, so by luring the female into close proximity, the male is then better able to position himself for mating to occur.
Ref: Kolm N., Amcoff M., Mann R. P. & Arnqvist G. (2012) Diversification of a food-mimicking male ornament via sensory drive. Current Biology [link]
When a honeybee dies it releases a death pheromone, a characteristic odor that signals the survivors to remove it from the hive. This might seem a supreme final act of social responsibility. The corpse is promptly pushed and tugged out of the hive. The death pheromone is oleic acid [a fairly complex molecule, CH3(CH2)7CH=CH(CH2)7COOH, where = stands for a double chemical bond].
What happens if a live bee is dabbed with a drop of oleic acid?
Then, no matter how strapping and vigorous it might be, it is carried “kicking and screaming” out of the hive. Even the Queen bee, if she’s painted with invisible amounts of oleic acid, will be subjected to this indignity.
Do the bees understand the danger of corpses decomposing in the hive? Are they aware of the connection between death and oleic acid? Do they have any idea what death is? Do they think to check the oleic acid signal against other information, such as healty spontaneous movement? The answer to all these questions is, almost certainly, No. In the life of the hive there’s no way that a bee can give off detectable whiff of oleic acid other than by dying. Elaborate contemplative machinery is unnecessary. Their perceptions are adequate for their needs.
Ann Druyan & Carl Sagan, Shadows Of Forgotten Ancestors: Who Are We?, What Thin Partitions
A recent study has shown that the domestic horse (Equus caballus) can recognise familiar humans through the senses of sight, smell and voice, and are able to use these independently to identify an individual even if one or two senses are compromised. This suggests that they build a multi-modal descriptive identity for familiar people in the brain. So be sure, if you go out to the field to bring in your horse and they carry on grazing regardless of your calls and your approach - as any horse person no doubt will have experienced - they know exactly who you are, but are choosing to ignore you with every one of their senses!
Ref: Lampe J. F. & Andre J., 2012. Cross-modal recognition of human individuals in domestic horses (Equus caballus). Animal Cognition Online First [link]