Guppies and the fruits of orange

21 05 2012

Why does a lure work? What makes prey move towards a predator?  How does a predator know what would make a good lure?  All these questions were answered for one circle of life in the streams of Trinidad.  An Australian Research team found prawns with orange dots at the center point of their pincers, and found them lying in wait rather than moving as they usually would. The researchers also found the prey of these prawns, Trinidadian guppies, to be coloured with specks and splashes of the same orange colouring. Female guppies mated on a regular basis with the most orange guppies, and less as the orange diminished. Guppies were also found to be less afraid of those prawns with orange pincers. What created this obvious bias for the colour orange? Read the rest of this entry »


The Dolphin Alliance

6 05 2012

Humans may be the smartest animals on the land, but who claims that title for the sea? Bottlenose Dolphins have been working together for centuries, hunting, raising young, and playing. The question then becomes can they interact with humans?

A group of fishermen in Laguna, Brazil have been fishing in their local bays for years, and so have bottlenose dolphins. The water in the shallow areas is murky, making fishing a slow daunting process for the fishers. On the other hand, murky water has no effect on the echolocation of the dolphins, but the mullet fish are fast and confusing in their schools. Over many years an alliance has formed between these two groups benefiting both parties.  The dolphins herd the mullet close to the fishermen, and then signal to the men to cast their nets. The fishermen catch for more fish, and those that were not captured are without the protection of their school.

It is hard to tell to what extent the dolphins understand what it is they are doing; do they know what the humans are doing? Or do they associate signalling with a slap of the tail or head, with making a net fall out of the sky and a good meal? The dolphin’s signaling, though, shows which direction the fish are traveling, and where the net should be thrown. This indicates the possibility of a higher understanding than previously thought.

The fishermen have been working alongside the dolphins for years, and have individually named each one. Interestingly though, only half of the dolphins in the area participate in the fishing with the humans. For the Brazilians, dolphins may be man’s new best friend.

Hello there, neighbour!

3 05 2012

Birds are usually depicted as competitors, challenging each other for a female, or a nest site. This is not the case, however, for a European bird the Great Tits create a neighbourhood around them, and nests work together for different situations creating a better environment for reproduction.

If you were a predator approaching a nest of a bird, would you feel threatened by a single angry bird dive-bombing you? Make sure that you are thinking in terms of yourself as either the size of a weasel or the bird the size of a flying terrier. Now think of five or six of these animals mobbing you. As the old saying goes, there is safety in numbers.

These birds do not have automatic friendships, but only start helping each other after about one year of being neighbors. This works well for the species of bird, because they are not migratory birds, and nest in the same place year after year. When a group of birds first nest, they tend to stick to themselves, until they trust each other and work together. Some birds desert their nests if they do not like the neighbouring birds. Because of this joining of forces, younger birds building nests for the first time are not as successful at reproduction as the older more settled birds.

I chose to write about the Great Tits because many people think of humans as the only animals who have what we call acquaintances. These birds occasionally change nesting areas, but the neighbouring birds do not follow.