- Researchers at South Africa's University of Pretoria have looked into the decadent life of Southern Africa mole rats and were surprised by their "survival of the laziest" tendencies. The truly ugly rodents live in societies where up to 40 percent of them only sleep and eat. When mating time nears, however, the fat and lazy moles are first in line.
The Damaraland mole rat (Cryptomys damarensis) is a native of Southern Africa, most commonly found in the dry Kalahari Desert. Here, they live large colonies, digging burrows beneath the hard and barren desert soil.
A team of researchers at University of Pretoria, headed by Michael Scantlebury, has taken a closer look at the strange communities and found that the mole societies are split into two groups. In an article published in the prestigious journal 'Nature', Mr Scantlebury divides the mole rats in one lazy and one industrious group.
In a mole rat colony, the industrious animals performed more than 95 percent of the total work, including digging barrows, looking for food and raising the offspring. Meanwhile, up to 40 percent of the colony is literally born to be lazy. The other group, which is much fatter than the industrious moles, are doing virtually no work, but requiring food from their comrades.
The lazy moles in fact are not degenerating or living an unhealthy lifestyle, the researchers found. They are evolutionary rewarded through the building up of their fat stores. When the right time comes, they are ready to use their stored energy rightly.
At the few occasions when it rains in the Kalahari Desert, the soil becomes moist and soft - ideal conditions to dig a new labyrinth of burrows and establish a new mole rat community.
"It is after these rare rain events - perhaps once or twice a year - that infrequent workers suddenly 'spring into action' and start digging," explains Mr Scantlebury. The lazy section of the moles becomes hyperactive. They escape their colony, laying the foundation of a new society where they become the leading mate. The digging process may cost them around half of their fat stores and still, it may be long before the newly active moles are in a position to search for food or being fed.
Having established a new network of burrows during the rainy season, the chance of finding a mating partner largely increases. Established mole rat colonies indeed are a sexually dry zone. The rodents count on one queen per colony, having one or two male lovers. These are the only ones having sexual relations in the entire colony.
The rest of the colony is mostly composed of close relatives, experiencing barriers against incestuous relations. Only occasional independent males from time to time pop by the colonies, where they may engage in short sexual affairs. These individual males however are exposed to high risks. Mortality rates are high as the slow and poorly sighted rodents are exposed to predators.
The lazy mules, however, have the best possibilities of survival and reproduction. Their inborn laziness constitutes a perfect energy balance regarding the climate of the Kalahari. The helpful workers in the mole rat colonies - all closely related to the lazy minority - thus assist in the long-term survival of the species' gene pool, the South African researchers conclude.
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