Historic First: Rare twinning in Asian Giant Tortoises at Nagaland Zoo

Guwahati: A zoo in Nagaland has etched its name in history for a ‘rare’ event.’

For the first time, twinning has occurred in the Asian Giant Tortoise (Manouria emys phayrei) which is critically endangered as per the IUCN Red List.

The northeastern part of India, located along the Indo-Myanmar hotspot, harbors a diverse range of species, including some of the rarest, within its pristine habitats. This region, where the eastern Himalayas and Indo-Burma hotspot converge, is globally recognized as a ‘Turtle Priority Area’ due to its exceptionally high species and taxon richness.

The Asian Giant Tortoise Manouria emys phayrei (AGT) is considered critically endangered as per the IUCN Red List. The species is traditionally known to inhabit the mid-elevational, wet, forest ecotones of Northeast India.

AGT is the largest tortoise in mainland Asia and weighs up to 36 kg.

The species faces mounting threats such as direct harvesting as well as habitat degradation such as slash-and-burn agriculture putting its survival in jeopardy. Manouria is the only genus of tortoise where females tend to show parental care.

The TSA Foundation India in collaboration with the Nagaland Forest Department established the country’s largest conservation-breeding facility for M. e.phayrei at Nagaland Zoological Park, Rangapahar, Dimapur, Nagaland, with the eventual goal of introducing tortoises into natural habitats.

On April 30, 2023, a large female (SCL 51 cm) laid a clutch of 53 eggs. After an incubation period of 74 days at temperatures of 23.9–33.7 °C and relative humidity of 50–99% (misting on alternate days) in a Styrofoam box filled with vermiculite topped with a layer of nesting leaf litter, 38 of the eggs hatched.

While assessing hatchlings, we noticed the development of twin embryos in two eggs. Two sets of twins emerged out of two eggs in July and they were nurtured very carefully using a teak leaf as makeshift shell in order to keep twins intact until they separated on their own.

This is a rare phenomenon in AGT and may be the first published record of twinning in AGT as per our best knowledge” Sushmita Kar who is doing Ph.d on the species and working with Turtle Survival Alliance India told EastMojo on the unique event.

“Twinning has been documented in both marine and freshwater turtles but there has been no twinning in either subspecies of Manouria emys, the study documenting the rare eventwhich has been published in Reptiles and Amphibians journal says.

“The weaker hatchling from each set of eggs did not survive long after hatching. Although smaller than their clutch mates, the stronger hatchlings from both sets of twins survived up to a significant amount of time. The twin pairs of Manouria emys phayrei documented in the current study shared characteristics noted in most other twinned turtles,including sharing a single yolk sac, differing sizes, and mortality of the smaller individual” she said.

The 176-hectare Nagaland Zoological Park, located in Dimapur District of Nagaland is recognized by the Central Zoo Authority of India. The Manouria emys conservation-breeding enclosure, established in 2018, covers 0.2 hectare with separate facilities for upkeep of hatchlings, yearlings, and adults.

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