Philadelphia Zoo announces historic births

The Philadelphia Zoo’s 2 oldest residents, Mommy and Abrazzo, who are estimated to be around 100 years old, welcomed 4 hatchlings. Mommy is currently considered one of the most genetically valuable Galapagos tortoises in the Association of Zoos and Aquariums (AZA) Species Survival Plan (SSP) and one of the oldest first-time mothers in her species.

Mommy at the Philadelphia Zoo (Image courtesy of the Philadelphia Zoo)

Galapagos tortoises can be found on the Galapagos Islands located in the Pacific Ocean right off the coast of Ecuador and are the largest living species of tortoises. A small Galapagos tortoise can grow to be about 500 pounds, and females can average around 250 pounds. Because they are cold-blooded, they spend 1-2 hours laying in the sun before spending another 8-9 just grazing and relaxing. It is estimated by scientists that these tortoises can live between 100-200 years, and there are only 13 living species native to 7 of the islands.¹

The hatchlings

According to the Philadelphia Zoo, the hatchlings are being held behind-the-scenes in the Reptile and Amphibian House, eating and growing appropriately, each weighing between 70-80 grams. Out of the 4, the first one hatched on February 27, 2025, and the team at the zoo continued to monitor the other eggs that could hatch following the first. Each of the hatchlings will make their debut to the Philadelphia public on Wednesday April 23, 2025, which is also the 93^rd anniversary of Mommy’s arrival to the Zoo.

“As an AZA accredited institution, we take great responsibility participating in the Galapagos Tortoise SSP and are thrilled for this successful pairing of Mommy and Abrazzo,” expressed Rachel Metz, vice president of animal well-being and conservation, in the organizational release.¹

“At one point, each of the Galapagos Islands had its own unique Galapagos tortoise, but sadly, several of them are now extinct. These hatchlings not only protect the species from extinction, but serve as important ambassadors to inspire guests to save wildlife and wild places.”

Each of the hatchlings are part of the AZA SSP breeding program, which works to help ensure the survival of this species while also maintaining a genetically diverse population. The Western Santa Cruz Galapagos tortoises are currently listed as critically endangered by the International Union for Conservation due to human-wildlife conflict, habitat loss, and the introduction of invasive species.¹ Besides the 4 born at the Philadelphia Zoo, the last clutch of these tortoises to be hatched in an AZA accredited zoo was at Riverbanks Zoo and Garden in South Carolina in 2019. Other zoos across the United States have also shared they have breeding pairs of the species, including Honolulu Zoo, San Diego Zoo, and Zoo Miami.

The 4 hatchlings at the Philadelphia Zoo (Images courtesy of the Philadelphia Zoo)

Galapagos Tortoises at the Philadelphia Zoo

Abrazzo was brought to the Philadelphia Zoo in December 2020 on a SSP breeding recommendation from Riverbanks Zoo and Garden. The Zoo then made donations on its Giving ZOO Day 2021 to buy a new substrate for Mommy to be able to lay her eggs in. The following year, the animal care team worked with its conservation education team to study the animals and create an ethogram of Abrazzo’s behaviors to see how he was spending his time. Then, starting in 2023, Mommy laid 4 clutches of eggs, with 3 resulting in no viable eggs, but this group of hatchlings came from the 4^th she laid in November 2024.¹

Typical female tortoises lay 2-20 white, hard-shelled, spherical eggs about the size of a billiard ball in a hole they dig, according to the release.¹ In November 2024, Mommy laid 16 eggs, and the reptile and amphibian team dug them up to incubate 8 as male and 8 as female. The sex of the hatchlings is determined by the incubation temperature, with temperatures below 82.4°F producing males and above 85.1°F producing females, and they hatch after 4-8 months. Each of the baby tortoises hatched were incubated as female in the Philadelphia Zoo.

“The Galapagos Tortoise SSP program is thrilled to help Philadelphia Zoo welcome Mommy’s offspring,” said Ashley Ortega, Galapagos tortoise SSP coordinator and studbook keeper at Gladys Porter Zoo in Texas. “This feat is even more incredible considering that Mommy is the oldest first-time producing female of her species in any US zoo. Prior to the hatchlings, there were only 44 individual Western Santa Cruz Giant tortoises in all US zoos combined, so these newest additions represent a new genetic lineage and some much-needed help to the species’ population. We are excited to learn more about how we can replicate this success at other accredited zoos since the team in Philly has accomplished something that was seemingly impossible.”

Philadelphia is home to 2 adult Galapagos tortoises, Abrazzo, Mommy, and another female, Little Girl, plus the 4 newest additions. The public will be able to see the 4 new hatchlings beginning on April 23. The hatchlings will remain at the Philadelphia Zoo for at least 5 years. After 5 years, the team at the zoo will work with the AZA SSP to determine if and when they will be moved to different facilities.

Reference

1. Four Critically Endangered Galapagos Tortoises Hatch at Philadelphia Zoo, First Successful Hatching of this Species in Zoo’s History. News release. Philadelphia Zoo. April 3, 2025. Accessed April 7, 2025. https://www.philadelphiazoo.org/news/four-critically-endangered-galapagos-tortoises-hatch-at-philadelphia-zoo/