Shrinking of Rhinoceros Horn

Context

• As per the Study by British Ecological Society, the horns of rhinoceroses may have become smaller over time.

Reasons for shrinking Horns

• Rhinos have long been hunted for their horns, which are highly valued in some cultures.
• The declining horn length over time across species, perhaps related to selective pressure of hunting and evolution.

Key Fact:

• Rhino horns are made of keratin, which is also the key component of human hair and fingernails. 

More about the Study

• The study found that the rate of decline in horn length was highest in the critically-endangered Sumatran rhino and lowest in the white rhino of Africa, which is the most commonly found species both in the wild and in captivity. 
• This observation follows patterns seen in other animals, such as tusk size in elephants and horn length in wild sheep, which have been driven down by directional selection due to trophy hunting.

Rhinoceroses

• About:
  • Rhinoceroses are large, herbivorous mammals identified by their characteristic horned snouts. 
  • The word “rhinoceros” comes from the Greek “rhino” (nose) and “ceros” (horn). 
  • There are five species and 11 subspecies of rhino; some have two horns, while others have one.

• Geographical Location:
  • White rhinos and black rhinos live in the grasslands and floodplains of eastern and southern Africa. 
  • Greater one-horned rhinos can be found in the swamps and rain forests of northern India and southern Nepal. 
  • Sumatran and Javan rhinos are found only in small areas of Malaysian and Indonesian swamps and rainforests.
• Threats:
  • Habitat loss and fragmentation
  • Poaching (especially for their horns and hide)
  • Reducing population density
  • Decreasing genetic diversity
• Conservation status of the five species are:
  • Javan Rhinos (Rhinoceros sondaicus): Critically Endangered 
  • Sumatran rhinos (Dicerorhinus sumatrensis): Critically Endangered 
  • Black rhinos (Diceros bicornis): Critically Endangered 
  • White rhinos (Ceratotherium simum): Near Threatened 
  • Greater One-Horned Rhinos (Rhinoceros unicornis): Vulnerable

Rhinos in India

• About:
  • Only the Greater One-Horned Rhino is found in India which is also known as the Indian rhino and is the largest of the rhino species.
  • Assam accounts for its largest population in India and had at least five rhino-bearing areas till the 1980s.

• Features:
  • It is identified by a single black horn and a grey-brown hide with skin folds.
  • They primarily graze, with a diet consisting almost entirely of grasses as well as leaves, branches of shrubs and trees, fruit, and aquatic plants.
• Conservation Efforts by India
  • New Delhi Declaration on Asian Rhinos 2019: Signed by India, Bhutan, Nepal, Indonesia and Malaysia.
  • National Rhino Conservation Strategy 2019
  • Project to create DNA profiles of all rhinos by the Ministry of Environment Forest and Climate Change (MoEFCC).
  • Indian Rhino Vision 2020.
• World Rhino Day is celebrated on September 22 every year.

Source:TH