Melody Lytle / Flickr

The Curious Case of the Phantom Hippo Teeth

By Laura G. Shields

Think of the illegal wildlife trade, and elephant tusks and rhino horns come to mind. But another of the world's largest land mammals is slipping under the radar: the common hippopotamus (Hippopotamus amphibius) may be at greater risk than previously believed, according to a new analysis of the international trade in hippo teeth.

Hippo ivory, from their large canines and incisors, is an affordable alternative to elephant ivory (international trade in elephant ivory is increasingly restricted). Its legal trade quotas are agreed upon by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). But when researchers looked into CITES trade records for an investigation recently published in the African Journal of Ecology, the numbers looked suspicious.

Lead author Alexandra Andersson, a conservation biologist at the University of Hong Kong, examined the export and import numbers for animals in the legal trade markets, and noticed the numbers didn't match up—sometimes dramatically so.

Hippo teeth, primarily used for ornamental purposes, are available for sale in a Hong Kong shop.Alexandra Andersson / University of Hong Kong

"I just thought that was a bit strange," Andersson told Mongabay. "So I decided to select one case study to dive deeper into this issue and find out why this happens, and how it's so prevalent in the CITES trade database."

She chose to investigate the hippo ivory trade, a straightforward case compared to other wildlife trades. Hong Kong imports more than 90 percent of global hippo teeth, largely from just Tanzania and Uganda.

When Andersson and coauthor Luke Gibson compared the trade volumes reported between Hong Kong and Uganda from 1995 through 2013, they found more than 14,000 kilograms (31,000 pounds) of hippo teeth were missing. Uganda reported exports totaling 79,000 kilograms (174,000 pounds), but Hong Kong reported receiving just 65,000 kilograms (143,000 pounds).

"This article is one of the first ones I've actually seen that takes CITES records numbers and says, 'Look, there's something really wrong here,'" said Pieter Kat, an evolutionary biologist and geneticist at LionAid in the United Kingdom, who was not involved in the study.

Hippo ivory is an affordable alternative to elephant ivory.Rhett A. Butler for Mongabay

The authors examined common bookkeeping errors as possible reasons for the mismatched data, but they struggled to identify the exact cause.

Their difficulty didn't surprise independent conservation biologist Allie Russo, who was not involved in this study. Russo has looked at the CITES database for multiple species, including parrots. She found there are too many shortcomings to make sense of the inconsistencies.

This disparity brings into question how effective the regulations are, said Kat. He believes CITES is badly in need of reform.

"If you are dealing with endangered species in trade, one of the first things you have to do is be really careful about accurately counting up the total number of specimens that you have in trade," Kat said in an interview. "There shouldn't be these discrepancies in the records."

For hippos, the authors estimated the missing teeth represent at least 2,700 individual animals. That's about two percent of the African census of 125,000 to 148,000 hippos, according to a population estimate from 2008. But hippos have been losing habitat, are poached for meat and ivory, and have conflicts with humans, so the survey needs updating, Kat said.

The current hippo population in Africa may be dramatically less than the 2008 estimated number of 125,000 to 148,000.Rhett A. Butler for Mongabay

Hippos are an easy species to count, he noted. From the air, their large purplish-gray bodies stand out along waterways. A new population estimate could change their IUCN and CITES conservation status.

The authors recommend supporting African authorities in their efforts to protect the species. Although the trade in hippo teeth was banned in Uganda in 2014, the country has far fewer than the recommended number of rangers per given area of protected land. That makes it easier for poachers to smuggle ivory to neighboring countries.

Such illegal ivory is a potential cause of the data mismatch, the researchers believe.

"It's so easy to fake permits and then ship illegal shipments under the disguise of being legal," Russo said. "It could be happening right under our noses. If we don't tighten up the data reporting mechanisms, it's just going to continue."

Hippos have large curved canine teeth and a pair of huge incisors in the lower jaw.Peripitus via Creative Commons (CC- BY-SA-3.0)

Reposted with permission from our media associate Mongabay.

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