By Janina Castro

According to the Facebook page of Wild Birds of BGC, the shaded walkway known as the BGC Greenway Linear Park is home to several resident bird species, such as the Collared Kingfisher, Olive-backed Sunbird, and Scaly-breasted Munia. Even some migratory birds, like the Brown Shrike, would visit this patch of greenery in the city.

I visited this path one morning to check out these birds, but much to my surprise, I met around a dozen of perky squirrels instead.

I watched them scurry through the treetops, hopping from branch to branch, and nibbling on the young leaves of the trees. Their acrobatic prowess and cute faces stole the show from the birds of BGC that day. However, these sneaky squirrels are not as uncommon as you think here in Metro Manila.

On July 6, 2020, the UP Wild posted a video on Facebook of a Finlayson’s squirrel in UP Diliman. They stated that this was likely the first documented squirrel in the area and could spell bad news for local wildlife.

This kind of squirrel has also been spotted in other parks and residential areas in Metro Manila, such as La Mesa Ecopark, Ninoy Aquino Parks and Wildlife Center, Forbes Park, Alabang, and Dasmarinas villages.

I sent a photo of the BGC squirrels to the UP Wild and they confirmed that these are Finlayson’s squirrels, too.

Adaptive. Invasive

The Finlayson’s Squirrel or Variable Squirrel (Callosciurus finlaysonii) is naturally found in Cambodia, Vietnam, Laos, Myanmar, and Thailand, as detailed in a 2019 article published online by Commonwealth Agricultural Bureaux International (CABI).

This squirrel prefers lowland forests, coconut plantations, and open woodland, surviving on a diety of fruits, nuts, and even young birds in their nests, according to Dr. Nielsen Donato in a 2014 video he uploaded to YouTube where he observed invasive squirrels.

There have also been recordings of Finlayson’s Squirrels in northwest and south Italy, Singapore, and Honshu in Japan. Although there’s no evidence yet that confirms how the squirrels ended up in Singapore and Japan, the Italy populations of squirrels startd when a handful of individuals were released in Aqui Terme, northwest Italy and Maratea, Basilicata region, southern Italy around the 1980s.

These Italian populations of squirrels have been increasing as they adapt themselves to their surroundings. Sadly, they are fast becoming invasive species in Japan and Italy because they can easily adapt to urban settings.

What makes a species invasive?

An invasive species is not naturally found in an area that it was introduced to and can cause harm to the ecosystem. These species hardly have any predators where they are introduced, making it hard to naturally balance out their population.

Though there are cases of urban predators adding invasive species to their diet, this may not be enough to keep their populations in check, according to a 2012 National Geographic online encyclopedia entry written by Kim Rutledge and team. Invasive animal species are not picky eaters and can learn to eat all kinds of new food in their introduced environment, sometimes even competing with native species for food.

Cute and dangerous?

These invasive squirrels have been observed to strip the bark off of trees in parks, making the trees more vulnerable to diseases since they no longer have their protective outer covering, according to a 2011 article by Sandro Bertolino and Peter Lutz published in the journal Mammal Review. There have even been cases of ancient trees needing to be cut down because they got sick from bark stripping activities.

There were also cases here in Metro Manila of the squirrels chewing on electric wires, as narrated by Donato in his YouTube video. Just like other invasive species, they can carry diseases and pathogens that can pass to native species and endanger local populations.

But all of this is giving the Finlayson’s squirrel a bad reputation.

We have to remember that they, and other invasive species, are just doing what they can to survive in a completely new environment. In the end, it was humans who released them into the wild and it should also be humans who need to be part of the long term solutions.

What can we do?

Bertolino and Lurz, in their research about invasive squirrels, emphasized that urgent and immediate actions should be taken as soon as squirrels are found in an area because, one they establish themselves, it can be very difficult to manage their population.

It is especially dangerous to local wildlife if the Finlayson’s squirrel manages to spread to protected areas and key biodiversity areas where they could bring greater harm to the environment.

1. Be a responsible squirrel parent

Prevention should take priority, so if you are already caring for a squirrel, be a responsible pet parent and never release them into the wild. Public education is also key, so you can talk about this with your friends and family!

2. Inform the right authorities

If you spot any squirrels in your area, you can report this to the Biodiversity Management Bureau of the Department of Environment and Natural Resources to let them know that a population may have established itself near you. Remember, these squirrels are considered wild animals, so directly handling them should be left to the professionals.

3. Keep biodiverse spaces alive

Supporting the presence of possible predators of the squirrel in the city can be one natural way to keep their population in check. Parks, cemeteries, and lush school campuses are examples green spaces where birds of prey, such as the Philippine Serpent Eagleand owls, as well as snakes, can safely live in the city so it’s important to preserve and push for more green spaces in the city.

Taking responsibility

Invasive species like the Finlayson’s squirrel can harm the local animals that we love and damage the vital trees of our parks, farms, and protected areas. Responsible pet owners, natural predators, and strong wildlife trafficking regulations all have a role to play in keeping the balance in our urban wild backyards. Even everyday animal lovers like you can help by keeping an eye out for squirrels in your area.

This appeared in Animal Scene magazine’s November-December 2020 issue.

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