Dave Taylor's African Safari: Trophic Level II - The Herbivores - Grass Rat

Dave Taylor's African Safari: Trophic Level II - The Herbivores - Grass Rat - Page 15

Trophic Level II - The Herbivores
Grass Rat
Page 15

Arvicanthis spp.

Length: 9-21 cm (3.5"-8")

Weight: 50-130 g (1.7 -4.6 oz.)

Tail: 22-32 cm (8"-12.5")

Habitat: Grass rats are found in grasslands and all types of savannas including grassy glades in forests. They are active during the day.

Food: Grass rats eat seeds, leaves and the shoots of grasses. They need the high protein of the seeds to assure successful breeding. Grass rats have been known to eat insects on rare occasions.

Social System: Large numbers of grass rats live together in colonies. They follow runs and may be seen during the day scurrying along these miniature trails. As many as 30 rats have been found in a nest. Theirs is a social system that is little understood.

Behavior: An average of four or five young are born in the litter. Females are sexually mature at two months of age and are full grown at five months. Gestation lasts 28 days. Conception of the next litter probably follows within days of the birth of the last litter. The life span is likely much less than two years. Most grass rats will fall victim to one of their many predators long before they reach that age.

Prolonged rainy seasons benefit the rats by increasing the length of their breeding season. In these good times, there can be over 400 grass rats per hectare (900 per acre). In drought, the number drops to less than 10 per hectare (25 per acre). Such fluctuations are the way of the small creatures on the plains.

Grass rats survive the seasonal grass fires by living in burrows where the fire’s heat does not reach them.

Predators: Often the rodents are overlooked in favor of the larger, more spectacular herbivores on the plains. This is unfortunate because they are an important part of the ecosystem. Rodents consume as much or more plant material than the larger herbivores do. Their biomass alone is overwhelming and would be even greater if it weren’t for the number and variety of predators that feed on them. These include owls, hawks, kestrels, storks, herons, secretary birds, shrikes, snakes, lizards, servals, caracals, jackals, mongooses, wild dogs, leopards and even baboons.

If it weren’t for the predators, rodents would overrun the grassland. Yet the rodents too, prey on other animals. Most mice, rats and ground squirrels are not above snacking on a locust or termite if they come across one. So rodents too, do their part in controlling animal populations.

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