Aestivation

File:Kadina-snails-climb-fence-0716.jpg

Introduced Theba pisana snails aestivating on a row of fence posts in Kadina, South Australia

Aestivation, alternately spelled as "estivation" particularly in the United States, refers to a period of dormancy in animals. This state is analogous to hibernation, but while hibernation is usually triggered by cold temperatures, aestivation is a response to arid conditions and extreme heat. This adaptive behavior allows various animals, from invertebrates to vertebrates, to endure the challenges presented by the hottest and driest parts of the year.

Evolutionary Perspective

Lungfish, which trace back to the Devonian period, are among the earliest known creatures to practice aestivation. The evolutionary advantage of this dormant state is evident in its continued presence in diverse species across millennia. It offers a mechanism to conserve energy and vital resources, ensuring survival in inhospitable conditions.

Characteristics

During aestivation, animals exhibit:

• Inactivity: A marked decrease in physical movement and activity.
• Reduced Metabolic Rate: Their metabolism significantly drops, conserving energy.
• Physiological Changes: Some animals might undergo physiological adjustments to reduce water loss or protect themselves.

Triggers

Aestivation is primarily instigated by:

• High Temperatures: Extreme heat can be detrimental to many species, particularly those without mechanisms to cool down efficiently.
• Dry Conditions: Aridity can lead to dehydration, making survival challenging.

Although aestivation commonly coincides with summer months, it's not exclusively a summer phenomenon. The primary determinants are environmental conditions rather than a specific season.

Animals Known to Aestivate

Aestivation is observed in a diverse group of animals, both in land-based and aquatic habitats:

• Invertebrates:
• Snails: Some species bury themselves in the ground, sealing their bodies with a mucus membrane to prevent desiccation.
• Lady Beetles: These insects find sheltered spots and enter a state of torpor.
• Vertebrates:
• Nile Crocodile: These reptiles dig burrows or find natural shelters to stay cool.
• Lungfish: They bury themselves in the mud, creating a mucus cocoon around them

Related pages

• Torpor
• Dormancy
• Hibernation