Assessment of Body Condition in African (Loxodonta africana) and Asian (Elephas maximus) Elephants in North American Zoos and Management Practices Associated with High Body Condition Scores

Thirty-four percent. That's the share of zoo elephants in North America that score at the very top of an obesity scale — one in three animals that, in the wild, would walk up to fifty kilometers a day. Hold that number for a moment. Then consider that it's actually the conservative version of the problem. Morfeld and colleagues set out to get a systematic picture of body condition across North American zoo elephants — not anecdote, not veterinary impression, but a population-level assessment. They evaluated 240 elephants housed in Association of Zoos and Aquariums institutions: 132 African elephants, known scientifically as Loxodonta africana, and 108 Asian elephants, known scientifically as Elephas maximus. The tool they used was a Body Condition Score index, or BCS — a five-point photographic scale where one is the thinnest and five is the fattest, with scoring based on standardized photographs submitted by each zoo. The results were stark. That thirty-four percent figure represents elephants at BCS five, the top category, interpreted as suggestive of obesity. But when you add in BCS four — overweight, not yet obese — the number climbs to seventy-four percent. Three out of every four zoo elephants in this sample were in an elevated body condition category. BCS three, the middle of the scale and the reference point for healthy, normal body condition, applied to only twenty-two percent of animals. And the lowest scores, BCS one and two, the thin end of the spectrum? Fewer than five percent of the entire population. True leanness, in this cohort, was vanishingly rare. Before getting into causes, it's worth understanding how these scores were actually produced, because the credibility of the whole analysis depends on it. For African elephants, Morfeld had previously developed and validated a five-point visual index using ultrasound measurements of subcutaneous fat. For this study, the team developed a comparable index for Asian elephants from scratch. Zoos submitted three standardized images per animal — side view, rear-angle, and rear — and trained assessors scored each set. The Asian index focused on three anatomical landmarks: the ribs, pelvis, and backbone. At BCS five, the backbone is invisible, and the area flanking it is rounded and filled in. At lower scores, bony prominences become progressively more visible. Three assessors scored forty sets of Asian elephant photographs independently. Percent agreement ranged from seventy-eight to eighty-five percent. Weighted kappa values — a statistic that accounts for how close a disagreement is, not just whether it happened — came in between zero point seven and zero point eight two, which the Landis and Koch scale classifies as substantial to almost perfect agreement. The Asian index was also biologically validated: serum triglyceride levels differed significantly across BCS categories, specifically between BCS three and BCS four or five, and between BCS four and five. The scores, in other words, track real physiology. They're not arbitrary. Now to the question that matters most for management: what actually predicts whether an elephant ends up at BCS four or five? Morfeld and colleagues used multivariable regression to test demographic, housing, and management factors simultaneously, and four variables emerged as the strongest predictors. The first is exercise, specifically staff-directed walking. The team categorized walking into levels, and the top level — fourteen or more hours of staff-directed walking per week — was associated with an odds ratio of zero point two one for elevated BCS. That translates to a seventy-eight point eight percent decrease in the odds of being overweight or obese. The sample in that highest exercise category was small, only eight elephants, but the effect was statistically significant and large. Fourteen hours a week is not casual activity — it's roughly two hours a day, every day. Below that threshold, the protective effect fades. The second predictor is the feeding schedule. Elephants fed on an unpredictable schedule — varied timing across a twenty-four hour period rather than consistent, clockwork mealtimes — had an odds ratio of zero point three one for high BCS, a sixty-nine percent decrease in risk compared to those on predictable schedules. That's notable because seventy-eight percent of the study elephants were on predictable schedules. The majority of zoos are running the higher-risk feeding model. Then things get interesting, and a little uncomfortable for how zoos think about animal welfare. The third predictor was feeding diversity — and it went the wrong direction. Morfeld and colleagues measured feeding diversity using a Shannon diversity index, which captures both the number of different feeding methods used and how frequently each was used. More diversity meant higher risk. The odds ratio was four point seven, meaning elephants exposed to a greater variety of feeding methods were roughly four point seven times more likely to be in the overweight or obese categories. This is worth sitting with, because feeding enrichment — puzzle feeders, scatter feeding, browse stations, varied presentation formats — is standard practice in zoo management and is generally considered good for animal welfare. The intuition is sound: varied feeding keeps animals cognitively engaged and mimics the complexity of wild foraging. But this study suggests that in practice, more feeding methods may mean more total food delivered. The team didn't measure the quantity or caloric content of food — that's a noted limitation — so they can't say definitively that diversity caused overconsumption. But the association is strong and consistent in the model. The protective effect of unpredictable schedules fits a parallel logic. Morfeld and colleagues suggest that irregular timing may suppress appetite hormones, lower serum insulin, and reduce fat deposition — mechanisms that mirror what's seen in intermittent feeding research in other species. Unpredictable feeding may also better approximate natural foraging patterns, where meal timing is genuinely variable. When feeding is predictable, animals may anticipate and over-consume. When it isn't, that anticipatory response is dampened. The fourth predictor was sex. Female elephants had an odds ratio of two point one five for elevated BCS compared to males — roughly double the risk. The sex-specific prevalence numbers make this concrete: BCS five was observed in thirty-three percent of African females and forty-eight percent of Asian females, versus seven point seven percent of African males and seventeen point four percent of Asian males. Asian females, in particular, were the most affected group in the entire study. The authors flag this as biologically interesting and note it warrants further investigation, but the study doesn't resolve why the difference exists. What the data do establish is that this is a population-level problem, not a collection of individual outliers. When seventy-four percent of animals across two hundred forty individuals in dozens of institutions score in elevated categories, that's a systemic signal. Individual variation doesn't produce numbers like that. The practical outputs of the study address this at two levels. First, the validated BCS indices — the existing African elephant tool and the newly developed Asian elephant index — give zoos a standardized, repeatable way to track body condition over time. A single score taken at one point is a snapshot. Repeated scores across months and years are a trajectory, and trajectories are what allow early intervention. The Asian index in particular is designed to be usable with standardized photographs or direct observation, which makes it accessible to zoo staff without specialist training. Second, the regression results point to specific, modifiable targets. Walking exercise above fourteen hours per week is achievable in well-resourced institutions and represents a concrete benchmark. Feeding schedule predictability is a policy decision — switching to unpredictable timing costs nothing and is associated with a sixty-nine percent reduction in elevated BCS risk. The finding on feeding diversity is more complicated, because it cuts against welfare intuitions, but it does suggest that zoos should track not just the variety of feeding methods but the total food volume those methods deliver. One additional finding is worth flagging. In the univariate analysis, the use of rewarding stimuli during training was associated with higher BCS — suggesting that treats used in keeper interactions may contribute meaningfully to caloric intake. That connection didn't survive into the final multivariable model, but it's a signal worth watching in future research. What's still unresolved is the downstream health question. High body condition was linked to ovarian acyclicity in one earlier study, and elevated insulin and leptin tracked with BCS in that work. But associations between BCS and musculoskeletal or foot health haven't been clearly established in the North American population. Longitudinal studies connecting BCS trajectories to reproductive, metabolic, and cardiovascular outcomes are the logical next step. For now, what Morfeld and colleagues have produced is both a diagnosis and a set of tools. The diagnosis: obesity-level body condition affects one in three North American zoo elephants, and elevated body condition affects three in four. The tools are validated scoring indices and a clear set of management levers — exercise volume, feeding schedule unpredictability, and careful monitoring of total food delivery — that the data associate with lower risk. For animals that can live more than sixty years in captivity, getting those levers right is a long-term welfare commitment. This lecture was created by ennepō. Go to https://ennepo.ai to Discover, Create and Follow the latest research in your field. Read when you can. Listen when you want to.