There’s something in the water, and it seems to be in the form of a rodent infestation. Recently, there’s been a minor plague of sophisticated, intelligent documentaries that look at rat-like creatures and how they shape culture, the environment and the people with whom they interact.

Last year’s tremendous ‘Rat Film’ illustrated beautifully the correlation between political segregation and the rise of vermin, while Morgan Spurlock’s horror-like ‘Rats’ looked at different vignettes where the creatures demonstrated their nefarious resilience. This year’s addition to the canon comes in the form of ‘Rodents of Unusual Size’, a film with a cheeky nod to ‘The Princess Bride’ that investigates the ways in which 20 lb. swamp rat creatures called nutria are being combated in southern Louisiana. Far more than a one-note piece, Chris Metzler, Jeff Spring and Quinn Costello trace the history of the non-endemic beasties and the affect they have on the coastline.

A holistic approach to the narrative sets the documentary apart. The fascinating piece immediately challenges expectations by proving that factors of unintended consequences – from the introduction of the animals to the U.S. to the supposedly environmentally friendly anti-fur movement – have all resulted in an issue that affects not only the region but coastal areas all over the world. These ROUSes offer a look into the complicated wave of animal and ecosystem interaction, and show that simple answers are extremely hard to come by for problems of this intricacy.

The pace is a bit strained at times, but the film is of sufficient scope and ambition to remain compelling. Thanks to charismatic subjects, from a long-time fisherman on the hunt to the inimitable Kermit Ruffins cooking up some fine vittles, the film provides a real sense of the kind of quirky and fascinating characters that litter this part of the world. This is an environmental film that does what so few manage to do – refusing to shy away from the harsher realities of the situation, where notions of conservation must often come at the cost of other sacrifices.

An unusually effective film about these very unusual nutria, ‘Rodents of Unusual Size’ is an exceptional work of non-fiction that illuminates as much as it entertains.