Philadelphia Zoo has witnessed a one-of-a-kind event. Four female tortoises hatched from eggs laid by a 97-year-old female tortoise named Mommy, making her the oldest first-time mother of her species in a US zoo. 

This centenarian mother is no ordinary tortoise but a member of the endangered Western Santa Cruz tortoises, a subspecies found on the Galápagos Islands. They are one of the world’s largest and heaviest tortoises, with some of them reaching up to six feet in length and weighing over 300 kilograms (>600 pounds).

Moreover, these fascinating creatures can live for over 100 years and reproduce for most of their lives. Still, over the years, the Galapagos tortoises have faced a massive decline in their population. Various sources suggest that the island was once home to 200,000 tortoises, but today, only about 17,000 of them are left. Among these, about 3,400 are Western Santa Cruz tortoises. 

“Prior to the hatchlings, there were only 44 individual Western Santa Cruz Giant tortoises in all U.S. zoos combined, so these newest additions represent a new genetic lineage and some much-needed help to the species’ population,” Ashley Ortega, who is involved in the Galapagos tortoise breeding program for the Association of Zoos and Aquariums (AZA), said.

The story of Mommy and Abrazzo

Increasing human activity in the Galápagos Islands has caused significant damage to the natural environment over the past 50 years. Not only the giant tortoises but several other species, including the Galápagos seal, sharks, and penguins—that are not found anywhere else on the planet — are now on the brink of extinction.

To protect the tortoise subspecies and restore their population, some Galapagos tortoises were brought to US zoos in the 1900s. Currently, the Association of Zoos and Aquariums (AZA) runs a captive breeding program to increase the tortoise population. Mommy is a part of the same program. 

She first arrived at the Philadelphia Zoo in 1932, but unfortunately, didn’t become a mother for 90 years. In 2022, she met Abrazzo, a male Galapagos tortoise who is about 100 years old and first arrived at the zoo in 2020. In the beginning, the elderly couple didn’t share a good chemistry, and the zoo team wasn’t even sure if they could mate.  

However, after some time, Mommy and Abrazzo finally began showing some love to each other, and as a result, Mommy laid her first batch of eggs in 2023 and then two more clutches later in the same year, but unfortunately, those eggs didn’t hatch. In November 2024, she laid her fourth batch, including a total of 16 eggs.

Since the sex of a tortoise hatchling is determined by the temperature at which an egg is kept before hatching, eight eggs were incubated above 29.5°C (85.1°F) to produce females, and the rest were kept below 28°C (82.4°F) to produce males. Four of the female eggs hatched this year, representing the first clutch of eggs hatched in a US zoo in the last five years.

“The last clutch of Western Santa Cruz Galapagos tortoises to hatch in an AZA accredited zoo was in 2019 at Riverbanks Zoo and Garden in South Carolina,” the Philadelphia Zoo team notes. 

More baby tortoises are on the way

The new tortoise babies will add genetic diversity and would lead to a much healthier and resilient population in the future.

“This successful outcome comes from years of hard work studying animal behavior and providing top-level care. Until now, Mommy’s genes were not represented in the AZA population, making these offspring extremely important in the protection of this species,” Lauren Augustine, curator of reptiles at the Philadelphia Zoo, said. 

Moreover, the zoo team is hopeful that the rest of the eggs will also hatch in the coming weeks, leading to a 20 percent increase in the Galapagos tortoise population in the US. This will prove to be a big boost to the ongoing breeding program.

While visitors at the zoo can see Mommy and Abrazzo, they’ll have to wait until April 23 to see the babies. On that day, the zoo team will celebrate the 93rd anniversary of Mommy at the zoo and also introduce the babies to the public for the first time.

“This is a significant milestone in the history of Philadelphia Zoo, and we couldn’t be more excited to share this news with our city, region, and the world,” the Philadelphia Zoo team said.