GRAND RAPIDS, Mich. (WOOD) — Months after a pygmy hippo attacked and killed a sitatunga, a medium-sized antelope, the John Ball Zoo, located in Grand Rapids, Michigan, has updated its protocols and procedures for introducing animals.

The internal review found that the attack was “likely due to individual animal behavior as zoo staff undertook significant efforts to be fully prepared before and during the introduction of the two animals,” the zoo said.

The attack happened in May during a controlled introduction between the hippo and a male sitatunga named Chopper. The two had visually been introduced in preparation for them to be in a new multi-species habitat together. Those meetings went well, the zoo said.

“Based on our team’s extensive research and the animal behavior we observed, we believed this would be a successful introduction,” Peter D’Arienzo, CEO of John Ball Zoo, said in a press release. “We are deeply saddened that the incident occurred, and very proud of the work our animal care team has done before, during and after this incident. We will continue providing excellent care for animals for the purpose of preserving wildlife and wild places for generations to come.” 

The review during 54 days, totaling 300 hours of introductions between the pygmy hippo and sitatunga, showed the vast majority of interactions were positive. 

The zoo has updated the protocols and procedures for introducing animals: identifying additional opportunities to modify the habitat to allow for enhanced safety, bolstering its introduction communication process to include additional reviews and reinforcing staff’s ability to provide input before and during introductions.

“At John Ball Zoo, animal welfare is our number one priority, and as an institution we continuously work to improve our protocols and procedures to reflect that,” D’Arienzo said in the release. “As with any internal incident, we investigate, learn, train and grow so we can continue providing the best possible care for our animals.”  

Pygmy hippos are new to the zoo this year.