We hear a lot about the many invasive species we have in Maine, from insects and plants to birds and mammals. Some are despised — like browntail moth because of the itchy rash and tree damage they cause — while others, like bigleaf lupine, are adored for their bright colors. Many invasives have been here since the first Europeans arrived, though we still see new threats to our native biodiversity regularly: emerald ash borer, an invasive beetle, was discovered in Maine in 2018 and is devastating to any stand of ash tree that it finds. I’ll always point out that cats (domestic cats allowed outdoors) are non-native and are the No. 1 anthropogenic cause of mortality in birds, killing more than 2 billion birds per year in the United States.

There is a new invasive mammal that has been knocking on Maine’s door for some years, and just recently seems to have kicked it down: the eastern cottontail. We’ve been getting quite a few questions recently from folks who have seen rabbits and asked for identification and wondered if they should be reporting their sightings.

It is important to pause quickly and define a few terms to make sure we are all on the same page. A non-native species is a plant or animal (or other organism) that has been introduced to an area where it does not naturally occur. Often, this introduction is done by humans, either accidentally or on purpose. There are many non-native species that we are not concerned about ecologically. Just look in the average flower garden, and you’ll find plants that are originally from all over the world. The concern arises when a non-native species starts filling the ecological niche of a native species, and because they don’t have their natural predators here or other controls, they will easily outcompete the native species. That is when we consider them invasive.

I want to emphasize that the unnatural movement of species, again, often done by humans, is a large factor in this problem. With our changing climate, we are seeing species that historically did not occur in Maine slowly moving north and now able to thrive here. Northern cardinals, tufted titmice, Carolina wrens and red-bellied woodpeckers have become common backyard birds across most of southern Maine, and they were essentially unheard of in Maine until the 1950s.

This gets us back to the eastern cottontail, a species of rabbit that is native to the eastern U.S., but one that historically never reached New England. In the early 1900s, eastern cottontails were introduced into New England states to supplement and increase hunting opportunities, but because of their quick rates of reproduction and high survivorship, they’ve become a problem for our native rabbits (in other words, they’ve become invasive). Our native “rabbits” are the fairly widespread snowshow hare, probably best known for their coats that change to white in winter, and the rare New England cottontail, a rabbit considered threatened or endangered in every state in which it occurs (including endangered status in Maine) due in large part to habitat loss and fragmentation, and competition from eastern cottontails. It was denied federal listing in 2015 because of the efforts underway (habitat restoration, public education, and reintroduction in small populations) to slow the decline of New England cottontails in their range, but this new and increasing threat from eastern cottontails is concerning.

I want to clarify one point, because some taxonomy sticklers will surely point out the difference between rabbits and hares. Maine’s snowshoe hares are technically “hares,” not “rabbits,” as they are in the genus Lepus, while New England cottontails are “rabbits” in the genus Sylvilagus. We colloquially refer to these collectively as “rabbits” but technically could refer to them as the family Leporidae. If we include pikas (which are not found in the eastern U.S.), we get the whole order of Lagomorphs. This is important, because it hopefully shows how closely related New England cottontails and eastern cottontails are, both in the genus Sylvilagus, though they are distinctly different species.

For decades, there has been a successful effort to keep eastern cottontails from Maine, but it seems the dam has broken in the last few years. While I’m sure the state has better records— the Maine Department of Inland Fisheries and Wildlife mentions a first population from Kittery in 2017 — a community science project we can all submit records to is iNaturalist (inaturalist.org), which now has at least 25 eastern cottontail records for Maine, all since 2022. There are more submitted at the genus level, since they are so hard to visually identify from New England Cottontails, but given the habitat requirements and rarity of the latter, I’m sure more of these are easterns. Though the two are very hard to tell apart, eastern cottontails have a white spot on their foreheads, and New England cottontails have a black edge around their ears and a small hard-to-see dot between their ears.

This is an interesting threat because of the widespread appreciation of “bunnies.” In fact, many of the eastern cottontails that are being reported in Maine are all centered around densely populated areas, especially Portland, and are likely ones that started as pets. Each Easter, or actually the weeks following Easter, brings a spike in the number of “bunnies” reported to us around the state. A cute pet for the holiday turns out to be a poop machine that then gets released into the wild. We’ve even had big floppy-eared bunnies dropped off at Maine Audubon’s Gilsland Farm in Falmouth, which we have to catch and bring to animal control.

The love for these non-native, invasive rabbits is similar to the love for invasive lupines. Maine once had a native species of lupine, but now the vast swaths of purples and pinks you see are all the non-native species, which ecologically provide little to no benefits to our wildlife. It will be interesting to watch as eastern cottontails continue to do what bunnies do and spread from their current strongholds. I can’t go out in Portland without seeing a cottontail or signs (droppings and plant nibblings) of their presence; their ecological impact will certainly become more noticeable with time.

Note: The Maine Department of Inland Fisheries and Wildlife collects rabbit sightings. You can report a sighting on the website: maine.gov/ifw

Have you got a nature or wildlife question of your own? It doesn’t have to be about birds! Email questions to [email protected] and visit www.maineaudubon.org to learn more about birding, native plants, and programs and events focusing on Maine wildlife and habitat. Maine Audubon Staff Naturalist Doug Hitchcox and other naturalists lead free bird walks on Thursday mornings starting at 7 am, at Maine Audubon’s Gilsland Farm Audubon Sanctuary in Falmouth.