In the animal kingdom, burrows are underground structures created by animals for a variety of purposes. Furthermore, it is also one of the many survival strategies and is supported by the discovery of ancient burrows dating back millions of years. Modern-day relatives of these animals continue to dig intriguing burrows.
In the Kimberley region of Western Australia, a particular species of monitor lizard, the Varanus panoptes digs very unusual nests.
The mouth of the burrow has a straight, sloping descend followed by a tight, downward-spiral consisting of 4-5 convolutions. The convolutions end in a terminal nesting chamber at the bottom of the burrow. The nest is quite deep too, descending to depths of over 11 feet. This helps minimize temperature fluctuations.
The incubation period of V. panoptes is around eight months; hence, the nest has to undergo scorching temperatures and torrential floods. Other factors, such as soil profile also affect the depth and structure of the nest.
Once the female has laid her eggs, it partially fills the entrance and upper parts of the burrow with soil. This is done presumably to keep animals such as snakes and rodents out. It is also thought to maintain a constant temperature inside the nest.
The helical nature of the burrows are also very unusual too; it is the first for any reptile. One of the hypotheses for its helical nature is to prevent intrusion of predators into the nest. The tight, spiral convolutions prevent larger predators from gaining access to the nest. It has also been suggested that these spiral help to maintain moisture (since reptile eggs are prone to desiccation).
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