The size of zoo-elephant enclosures may be less important to the animals than social interaction and opportunities to engage with their environments.
That was one of the surprising findings in the largest study yet undertaken on zoo-elephant welfare.
Multiple academic institutions and accredited zoos cooperated on nine studies that have been gathered in one research collection, just published in the journal PLOS ONE.
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More than 200 Asian and African elephants from 68 accredited North American zoos were documented by the researchers, who studied the creatures' physical health, behavior, female reproduction and walking space.
One of the key findings concerned the elephant's living quarters.
"We expected to find associations between the size of zoo exhibits and welfare," said Cheryl Meehan, the study collection's lead author, a veterinary medicine research associate at the University of California, Davis.
"But space ended up being of minor importance when compared to social factors and management practices such as enrichment programs," she noted, in a statement.
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Elephants that were allowed to engage in enrichment programs such as using "puzzle feeders" – requiring the animal to put some thought and effort into reaching its food – were more likely to have healthy reproductive function, the scientists found.
The researchers said such practices could particularly help African elephants, which often have reproduction issues.
Meanwhile, social interaction too seemed to be another important factor in zoo-elephant welfare. Too much time alone, the scientists said, puts the animals at behavioral risk, while interaction with others in bigger social groups – especially those containing young animals – was a positive for elephant health.
Among the behavioral problems documented in the study concerned actions that are commonly associated with "compromised" welfare in the animals. One such behavior is the physical motion of swaying or rocking. That was seen in 75 percent of elephants studied, the researchers said.
Pinpointing the exact causes of the behavior can be difficult, though, the team said.
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