In the spirit of World Great Ape Day (September 9, 2017), we hope you enjoy this peek at one way we monitor the health of our energetic, charismatic bonobos. How do you take a bonobo’s blood pressure? It sounds like the start of a lame joke, but it’s actually a real question the San Diego Zoo bonobo keepers had to figure out. Last year we began participating in a blood pressure monitoring study for the Great Ape Heart Project. Just as in humans, cardiovascular disease is one of the main causes of death of apes in populations that can be examined, and we suspect that high blood pressure is a major underlying cause. Being able to detect high blood pressure in bonobos would allow us to initiate preventive care as well as treatment at a much earlier stage and prevent or slow the progression of the disease, resulting in longer and higher-quality lives for the animals. That’s all great in theory, but how—you must be wondering—do you get an awake blood pressure reading from a highly intelligent and dangerous animal? And here’s the answer: you just ask them! Well, okay, it’s not initially as simple as that because first you have to train them how. So the next question is, how do you train a bonobo to let you take their blood pressure? Here at the Zoo, operant conditioning training with the apes is an important aspect of their care, and one of my favorite ways of interacting with the animals. Through the use of positive reinforcement (usually high-value food items like fruit, baby food, and juice), the apes at the Zoo are trained to voluntarily take part in their own care by participating in a range of veterinary and husbandry procedures. They voluntarily present body parts for examination, shift from one enclosure to another, and allow keepers to treat wounds and even give injections. Training for blood pressure readings consisted of first getting the bonobos to present their hand through the mesh in the correct position; then to allow us to wrap the blood pressure cuff around a finger and apply pressure as the cuff inflated; and then to sit calmly and quietly, and hold position for 60 seconds while we obtained an accurate reading. That last bit has been the biggest challenge by far—anyone who’s ever met a bonobo knows they are anything but calm and quiet by nature! Luckily for us, we have some rock star trainees in our bonobo group (specifically 8-year-old Maddie, 10-year-old Mali, 13-year-old Makasi, 16-year-old Vic, 25-year-old Erin, and 43-year-old Loretta), and they began picking it up more quickly than we anticipated. With such distinct personalities, each individual learned at a different rate with slightly different methods. Vic, Makasi, Erin, and Mali are particularly focused and engaged trainees, and they progressed very quickly through the training process. Loretta, on the other hand, is a little harder to keep focused. (Being the matriarch comes with a lot of responsibilities, and sometimes she simply can’t be bothered to sit quietly for such a long period of time.) So, it took her a little longer to master the fully trained behavior. Maddie, our youngest trainee, is sharp as a tack, but still uncomfortable being separated from her mother, Lisa, and three-year-old sister, Belle, so Maddie’s training sessions have to be done with all three of them present. This proved problematic at first as the more bonobos there are around, the more opportunity there is for distraction, and it turns out that it’s particularly difficult to participate in a training session when you have a baby bonobo bouncing on your head. It was hard not to laugh at poor Maddie, with one hand presented through the mesh for her blood pressure reading and the other protecting her head from the hammering feet of her pesky little sister. Luckily for her, we were able to solve this problem pretty quickly by getting the help of an extra keeper to keep Lisa and Belle occupied during the training sessions, so Maddie could concentrate on the task at hand without worrying about baby bonobo attacks. With the help of one of the zoo’s veterinary technicians, the bonobo keepers are now able to get routine monthly blood pressure readings from six of the nine bonobos at the zoo. (We hope to eventually get regular readings from the other three, but based on their current maturity and concentration levels, we’re not holding our breath just yet....) This program has been an exciting process, full of challenges and surprises, and we’ve learned a lot along the way about training, heart disease, and the individual animals in our group, who never cease to surprise us. After more than a year of practice, the bonobos are getting better and better at correctly performing this behavior on command, but even our best trainees are sometimes more interested in somersaulting, screaming, and bonobo handshakes than a quiet training session. They are bonobos, after all! Rachel Bronstein is a keeper at the San Diego Zoo.