For the herd of elephants at the San Diego Zoo Safari Park, family isn’t just the main thing. It’s everything.

Two lactating African elephants—Umngani (pronounced OOM-gah-nee), who gave birth to a healthy female calf, Mkhaya or “Kaia”, on Sept. 26, 2018; and Ndulamitsi, known as Ndula, who gave birth to a healthy male calf, Umzuli-Zuli or “Zuli,” on Aug. 12, 2018—are participating in a nutritional study, allowing researchers to study the content of their milk.