Little Otter Meets Giant Otter

Have you ever wondered how one otter species would react if it met another? I did, and for a long time.

Peru is fortunate to count no fewer than three otter species among its fauna. There’s the diminutive and frisky gato del mar, or ‘cat of the sea,’ a.k.a. the marine otter (Lontra felina), which, as its name implies, occurs along most of the country’s coastline.

There’s the impressive lobo de rio or ‘river wolf,’ known to English speakers as the giant otter (Pteronura brasiliensis).

And there’s the elusive Neotropical otter or nutria (Lontra longicaudis).

I’ve been lucky enough to see all three, many times, on beach camping trips and during our fieldwork in the rainforest. But only once have I witnessed an encounter between two of these species.

The Neotropical otter and the giant otter have similar distribution ranges in Peru’s Amazonia, although Neotropical otters have been observed at altitudes above 3000 metres, while giant otters have never been recorded higher than 600 metres above sea level. And while the giant otter frequents both still as well as running waters, in the Madre de Dios region where my husband and I carried out our research, the Neotropical otter shows a very marked preference for streams and rivers.

It was on one of these small rivers that a Neotropical otter bumped into its larger relative. I had envisaged all kinds of lurid scenarios in the event of such a meeting. It wouldn’t have surprised me, for example, if the giant otter had given the little one a severe beating or even a fatal bite. Instead, as the two approached, swimming in opposite directions and apparently oblivious to one another, the Neotropical otter suddenly, with a short, sharp gasp, dashed up the river bank a couple of metres and stopped in its tracks. It stood there for about ten seconds, quietly watching as the giant otter passed by, then ran back into the water and continued on its way. The giant otter, meanwhile, did not deign to acknowledge the presence of its cousin in any way as it swam upriver, though I have no doubt it was acutely aware of it. Sadly, I don't have a photo of the encounter (we were too busy trying to remain unnoticed), but the whole routine seemed almost practised, familiar to both.

It is widely believed that competition between the giant otter and the Neotropical otter is avoided due to differences in preferred habitats, periods of activity, and dietary requirements. Giant otters tend to live in groups and fish together, the Neotropical otter is more of a solitary hunter. The Neotropical otter is generally assumed to be active mostly at dusk and dawn. In fact, we have found that, where the species is not persecuted by man, it may be seen at any time of the day. Research in other countries has shown that Neotropical otters eat smaller fish and that they supplement their piscivorous diet with crustaceans. In our study, we found that fish species overlap between giant otter and Neotropical otter diet is substantial but that the nutria indeed tends to consume smaller fish. And our observations of tracks showed that both species visit each other’s dens and latrines, suggesting interspecific signalling of the use of resources.

I will leave you with this screen shot of a brand new e-book by the IUCN/SSC Otter Specialist Group. It is available for download, free of charge, here.