Creature Feature: Invasive Impact

March 09, 2025| Education, Environment

By: Patrick Krudop

Welcome back to another edition of Creature Feature, where we explore the diverse wildlife that calls Lake Hopatcong and New Jersey home. Whether you are a regular reader or tuning in for the first time, feel free to check out past articles (a few are linked below) that have highlighted a varied portfolio of creatures and critters.

This time around, we’re focusing on a pressing issue facing New Jersey’s ecosystems: invasive species. These non-native animals, plants, and organisms can have a significant impact on local habitats, often outcompeting native species and disrupting the balance of our environment. While they may not always be easy to spot, invasive species are making their mark on New Jersey’s wildlife in ways that can affect both the natural world and our communities.

Today, we’ll be going over some basic information on each of these species, and if you are interested in reading in further depth about any of the invasive species covered, feel free to consult the New Jersey Department of Environmental Protection’s (NJDEP) Aquatic Invasive Species Management Plan and Invasive Species Management Plan for more information. 

Now without further ado, let’s dive into this month’s Creature Feature and take a closer look at these uninvited guests!

Emerald Ash Borer

If you've visited Hopatcong State Park, you may have walked the former Morris Canal towpath and noticed dead or dying trees along the way. The culprit? The emerald ash borer (Agrilus planipennis), a small but destructive insect native to northeastern Asia. Originally, these pests would mainly target already weakened ash trees, but in North America, they have a devastating ability to infest and kill healthy ash trees.

Since first being discovered in Michigan in 2002, emerald ash borers have spread across much of the United States, including New Jersey. Their larvae feed beneath the bark of ash trees, disrupting the flow of water and nutrients, causing the tree to die. What makes them especially dangerous is that they have no natural predators here, allowing their population to grow unchecked. In fact, tens of millions of ash trees have already been killed in the U.S. alone, and it’s estimated that without intervention, the infestation could lead to the loss of nearly all ash trees in affected areas.

In New Jersey, the damage is becoming increasingly evident in forests, urban landscapes, and parks like Hopatcong State Park. The presence of these invasive insects poses a significant threat to the state’s biodiversity and tree canopy. Strategies are being developed to manage the spread of emerald ash borers through monitoring efforts, tree removal, and sometimes chemical treatments, but the challenge remains ongoing.

As you walk through areas affected by the emerald ash borer, keep an eye out for signs of infestation, such as distinctive “D”-shaped exit holes in the bark or a general decline in tree health. Early detection and action are key to helping slow the spread of this invasive pest.

If you believe one of your trees at home might be infested with emerald ash borers, visit the official New Jersey Department of Agriculture website to find out what you can do!

New Zealand Mud Snail

Although not currently present in the Lake Hopatcong area, the New Zealand mud snail is worth mentioning due to its incredible invasiveness. This tiny snail is capable of asexual reproduction, allowing it to clone itself and rapidly increase its population. Under ideal conditions, a single individual could produce a colony of up to 40 million offspring in one to three years. The mud snail has earned a notorious reputation for completely choking out waterways, altering ecosystems in profound ways. With no natural predators that can effectively control their numbers, they often dominate large portions of aquatic environments, outcompeting native species and disrupting local biodiversity.

Native fish species may attempt to consume mud snails, but their tough, calcified shells and a protective "lid" called the operculum make them difficult to digest. The operculum can close so tightly that the snails pass through the fish's digestive system completely unharmed. This defense mechanism not only protects the snails but also provides no nutritional value to the fish, leaving them to expend energy in a futile attempt to feed. As a result, fish populations suffer, and the overall health of the aquatic ecosystem is negatively impacted.

The proliferation of the New Zealand mud snail poses a serious threat to the balance of freshwater ecosystems in New Jersey and beyond. Efforts to control their spread have been challenging, as the snails can hitch rides on boats, fishing gear, and even the shoes of unsuspecting humans. Preventing their spread requires increased awareness and active measures, such as cleaning equipment and adhering to best practices for preventing the introduction of invasive species. Remember to always clean, drain, dry when partaking in any recreational activities in New Jersey’s freshwater bodies. Without significant intervention, the mud snail may continue to wreak havoc on local waterways, outcompeting native species and causing long-term environmental damage.

Spotted Lanternfly

The spotted lanternfly, native to China and Southeast Asia, has become an invasive pest in New Jersey within the past few years, causing significant concern. This insect feeds primarily on the sap of trees, particularly the tree of heaven (which is also an invasive plant species), but also targets fruit trees, vines, and other plants. As it feeds, the lanternfly excretes a sticky substance called honeydew, which promotes the growth of sooty mold. This mold suffocates plant leaves, reducing their ability to photosynthesize and weakening the plants. Over time, repeated feeding can cause severe damage, even leading to plant death. With few natural predators in the area, the lanternfly's population can grow unchecked, making it a major threat to local ecosystems.

The economic impact of the spotted lanternfly is substantial, particularly for agriculture. Vineyards, fruit orchards, and timber industries are all at risk, as the lanternfly damages crops and reduces the quality of fruit. In New Jersey, the wine industry is especially vulnerable, with the pest potentially reducing grape yields and quality. The lanternfly also threatens local forests by weakening or killing trees.

Controlling the spread of the spotted lanternfly has proven difficult, as it can easily hitch rides on vehicles, outdoor equipment, and firewood. The insect's egg masses are hard to detect and remove, contributing to its rapid spread across the region. To help combat the invasion, New Jersey residents are urged to inspect their vehicles and equipment for egg masses, report sightings to local authorities, and use methods like tree banding and insecticides where appropriate. Without continued awareness and action, the lanternfly could continue to harm both the environment and economy of the state.

European Starling

If you’ve ever witnessed a group of European starlings (Sturnus vulgaris) flying together in a murmuration, you’ve likely been mesmerized by their synchronized movements. The sight of these birds, often resembling a dark, shifting cloud, is truly captivating. However, beneath their beauty, the European starling is an invasive species that has become abundant in New Jersey.

In addition to their overwhelming numbers, starlings pose a threat to native bird species. During breeding season, starlings are known to engage in nest parasitism, where they lay their eggs in the nests of other starlings. This is done in an attempt to have a different female raise their young. 

With a diet that includes almost everything, the vast amount of starling there are can contribute to a lack of food for our native species. As of now, this is not an issue, as they are frequently spotted foraging with robins, sparrows, grackles, crows, and cowbirds; however, if the population of starlings continues to grow, this could become problematic in the future.

While their environmental impact is concerning, starlings are also the subject of scientific study due to their unique behavior involving something called scale-free correlation. This phenomenon occurs when a small change within a system can trigger significant effects throughout the entire system. A good way to understand this is by comparing it to the “telephone game”, where a message is passed along a line and often becomes distorted. Where humans may find difficulty in passing along the same message down a line of people, starlings perform this expertly with a stunning level of accuracy. In starling flocks, a change in one bird’s speed or direction can quickly ripple through the entire flock, influencing its neighbors in a coordinated, almost hive-like manner. This makes their murmuration appear as though the birds are moving as a single, unified entity.

But why do starlings move in such a coordinated way? The formation of these dense flocks, or murmuration, serves as a defense mechanism against predators, particularly peregrine falcons. If you observe a murmuration in the wild, pay attention to the densest part of the group. Chances are, you'll find a raptor lurking at the edge of the flock, trying to pick off an individual bird. The tight clustering of the starlings makes it harder for predators to target a single bird, offering protection through sheer numbers and confusion.

Canada Goose

Could we write a Creature Feature on invasive species without mentioning the Canada goose? If you live near Lake Hopatcong or any water body in northern New Jersey, you know these birds well. They’re hard to miss—especially when honking their way across the sky in that signature V-formation. But that V isn’t just for show—it helps them conserve energy during migration. The lead goose takes the brunt of the wind resistance, and as the flock flies, the geese rotate positions so everyone gets a turn at the front.

However, as charming as their flight may be, Canada geese have become an invasive species in New Jersey, and their impact on the local environment is anything but welcome. Though the term “invasive” is often used for non-native species that cause damage to an ecosystem, these geese are a special scenario as they have become permanent residents rather than the transient visitors they used to be, especially around areas like Lake Hopatcong. The real problem? Their droppings, which are everywhere, contain high levels of phosphorus. This nutrient washes into the water, fueling algae growth and contributing to harmful algal blooms that threaten water quality and fish health. The geese also trample sensitive vegetation along the shore, disturbing the delicate ecosystems that rely on these plants for shelter and food.

To help discourage Canada geese from making your waterfront property their home, there are several steps you can take. One of the most effective methods is creating a shoreline buffer with native plants along the water’s edge. Geese prefer wide-open, grassy areas to graze, so planting dense vegetation or shrubs can make the area less attractive to them. Additionally, avoid feeding the geese as it encourages them to stick around. They’re opportunistic feeders and providing easy food sources can quickly turn your property into their dining spot. Installing low fencing or using decoys like predator figures (such as coyotes or owls) can also help to create an environment that geese find less hospitable, prompting them to look elsewhere for a more inviting place to land. By making simple changes to your landscape and habits, you can help keep goose populations in check.

While the Canada goose might be an iconic part of our skies, its impact on local ecosystems cannot be overlooked. Their presence serves as a reminder that even the most familiar creatures can have a ripple effect on their environment.

Invasive species are a common sight at Lake Hopatcong and throughout New Jersey. Recognizing them and taking action when possible can help reduce their impact on the environment.

Whether you’re a seasoned naturalist or simply curious about local wildlife, there’s always something new to discover about the fascinating creatures that call Lake Hopatcong home (welcome or not!). Every footprint, from the tiniest to the largest, helps shape the vibrant life of our lake, and even the smallest presence can have a big impact.

I hope you’ve enjoyed learning about these invasives that we may have at Lake Hopatcong. Perhaps this article has inspired you to explore the wonders of nature further, whether by reading a book, visiting a website, or simply stepping outside! If you have any wildlife photos from Lake Hopatcong, or if there’s a critter you’d like to see featured in an upcoming Creature Feature, please send your submissions to info@lakehopatcongfoundation.org. See you next time!