Monday, April 11, 2011

Follow the Leader

INTRODUCTION: Cattle are found on every continent in the world except that of Antarctica [1]. They are grass eating ruminants that provide milk and beef to people across the world [3].TheBubulcus ibis, or more commonly known as the Cattle Egret, is a type of heron. They feed exclusively on insects such as grasshoppers and crickets. These birds are originally from Africa and Asia, but can now be found in North and South America [2]. They are of medium size for a bird with a swollen throat, dark legs and feet, and short thick necks [2].These herons, along with various sub species of Bos primigenius, engage in a commensal relationship Where there are cattle, or even lawn mowers, there are Cattle Egrets. These birds will follow just about any animal or object that disturbs grasses where they feed.

RELATIONSHIP: The cattle Egret is a forager, following or riding on grazing animals and eating the insects that are aroused by the grazing cattle [2]. They can sometimes be seen hunting like other birds, but most commonly they follow cattle and what is stirred up [4]. The cattle typically do not gain anything from their interaction with the birds; they simply go about their grass eating. The key word here is typically. The Cattle Egret has been observed perched on top of cattle eating insects and or parasitic threats to the grazing animals [4]. This makes this relationship partly materialistic. Sometimes the birds are seen gaining food while simultaneously providing protection for the cattle, however more times than not, this is not the case and the cattle neither benefits or is harmed by this interaction.

COSTS AND BENEFITS: The costs and benefits for both participants of this relationship are minimal.

Cattle Egret: Cost: Egret is dependent on cattle for primary source of food. Benefit: Egret saves energy by not expending it on searching for food. Why benefit outweighs cost: The cattle egret typically has a clutch size between 1 and 9 [2], but many times the egret parents cannot keep up with the feeding demands of all their young and several may die [4]. It thus becomes extremely important for the Egret to conserve as much energy as possible so that the maximum number of offspring can carry genes to the next generation.

Cattle: Cost: Having a small animal stalk you all day. ARKive video - Cattle egrets following African elephants to catch flushed out prey Benefit: Every once in a while having the Egret eat something that is attempting to eat you. Why the benefit outweighs the cost: Even though the Egret hardly ever is found picking bugs off of the cattle themselves, it could happen, which would undoubtedly be a benefit of pest protection. But since the birds don’t cost the cattle anything, and cattle don’t eat birds, it is not worth the energy of the cattle to attempt to get rid of the birds.





5. Video:


  1. In relation to the cleaner fish and the fish they clean there was a signal given by the fish to allow the cleaner fish to enter the mouth of the fish. Does the grazing animals give a signal to the bird to allow the bird to land on the grazing animals?

  2. Not that I have read of. All of the sources that I have managed to come across mention this bird as one with niche following the animals. If i had to make my own guess about it, I would say that in the case of the large grazing animals, the birds may be flying to sit on the animal to get a view of the surroundings.My guess as to the reason that they choose not to always feed on top an animal is that bugs from the ground are more numerous and pleasing.