Horseshoe Island, located just offshore of Little Beach on the southern edge of the Little Egg Inlet, is teeming with wildlife again this year. Last year, under a five-year Management Rights Agreement secured from the state’s Tidelands Resource Council, the site was closed to the public from March 1- September 30 to benefit wildlife, in particular endangered and at-risk beach nesting birds and migratory shorebirds. The seasonal public closure of the island and its surrounding tidal areas is in place again this season.
Aerial view of Horseshoe Island Courtesy of New Jersey Fish and Wildlife
If you follow us or any other wildlife organizations on social media, you may have noticed that our posts these last few days have been inundated with amphibians. It may seem like odd timing, given that our early breeders (wood frogs, spotted, and Jefferson salamanders) completed their crossroad migration last month. But the reason is simple – it’s Amphibian Week!
Close up of an American toad that hitched a ride during this year’s crossing. Photo Credit: Nikki Griffiths
Globally, amphibians are disappearing faster than any other vertebrate group. The International Union for the Conservation of Nature (IUCN) estimates that 41% of amphibian species categorized for their Red List are currently facing extinction. That estimate is likely conservative, given that these creatures are often small and difficult to survey, rendering many species data deficient. This is concerning from multiple perspectives. From an ethical standpoint, we don’t want any wildlife to go extinct except maybe, in my extremely biased opinion, certain types of ticks… (I began my career as a moose technician and saw firsthand the terrible consequences that winter ticks have on these behemoths). Beyond that though, amphibians are tasked with a lot of responsibilities and carry out their work efficiently and without complaint. The list is inexhaustive but here are a few things that amphibians are doing for us and our planet as we speak: filtering water, sequestering carbon, eating pests (like mosquitos!), serving as prey for countless predators, helping researchers study regeneration (with hopeful applications to the future of organ transplants), aerating the soil in your garden, indicating where water sources have been contaminated by pollutants, and giving everyone who meets them a reason to smile.
For the second year in a row there haven’t been eagles nesting on the Three Bridges platform in view of eagle cam. The pair used the platform when it was first installed in 2021 and viewers got to watch the two chicks grow up and fledge. In 2022 & 2023 the pair have nested in a tree nest instead of the platform. While it’s disappointing that the pair didn’t use the platform, there was still plenty of avian action at the tower this season. There were several immature eagles visiting the platform this season, perhaps in the next few years one of these eagles will pair up and use the platform.
Slideshow: Highlights from the 2023 Three Bridges Eagle cam season
December 4th, 2022, photo by: Mary Ellen Hill
December 9, 2022; photo by, Barb McKee
eagle pair chase off Red- tailed hawk
American Kestrels
Peregrine Falcon
Red-tailed hawk
Northern Flicker
The eagle cam will be turned off April 1st.
Thank you to all the viewers who watch and enjoy this eagle cam. During the 2023 season there were 22,981 views of the cam. Thank you to the the eagle project volunteers, especially Mary Ellen Hill, who grab screenshots from the cam. We also thank PSE&G for hosting and supporting the eagle camera.
We’ve made it to the final “super species” in our “superhero” series though, like in the last post, we’re spotlighting an adaptation that aligns with one of the more notorious residents of Gotham City. Our local frog has all the chill, while this DC villain needs to chill… quite literally, as his sub-zero body temperature must be maintained to ensure his survival. Cryogenics expert, Dr. Victor Fries- better known as Mr. Freeze, had admirable intentions when he began his experimentation with ice. Unfortunately for him, accidental exposure to chemicals altered his physiology, necessitating the use of an air-conditioned suit and spurring a life of crime motivated by tragic desperation. The compound responsible for his transformation is thought by some to be glycerol, which also happens to be the key to the winter survival strategy of our favorite early breeding anuran- the wood frog (Lithobates sylvaticus).
Animals living in temperate climates must find ways to cope with the cold temperatures and reduction of food resources, characteristic of the winter season. Some species deal with winter by not dealing with winter… instead they migrate to milder conditions farther south. This is a path commonly taken by birds. Other animals have adapted to have a large body mass. This reduces their surface area and enables them to hold onto heat more efficiently. As a former moose biologist, I’m happy to give them a quick nod here. Many strategies exist across the natural world to increase the odds of persistence, but we’re here to talk about amphibians and, it’ll probably come as no surprise to you that they aren’t employing either of the aforementioned tactics.
Wood frogs are a vernal pool obligate species; they must have access to these temporary wetlands in order to breed and complete their lifecycle, but they don’t live in them all the time. Therefore, we do refer to them as migratory, but they only cover about ¼ to ½ mile during this annual pilgrimage, so temperature differences are negligible. Most frogs and salamanders in New Jersey endure the colder months by entering brumation- the “cold blooded” equivalent of hibernation. In this state, animals can drop their body temperature and metabolism to conserve energy. Some species burrow and use the ground as insulation. Others brumate in streams and ponds since water cools at a slower rate than air. Wood frogs cover themselves in leaf litter (for camouflage) and spend the winter comfortably as frog-cicles. That’s right- they essentially freeze solid and thaw once air temperatures become favorable again.
Under normal conditions, when a cell freezes, ice crystals form internally. These solids can then expand, which damages organelles and ultimately ruptures cell membranes. This leads to cell death. Compounded by damage incurred in blood vessels and dehydration, this would be a fatal situation for most animals. Wood frogs have found a hack to get around these devastating consequences.
A recently thawed wood frog huddled beneath a leaf. Photo credit: Nikki Griffiths.
As temperatures drop, wood frogs continue to produce urine but cease voiding it. Instead, the urine is concentrated into urea, which floods the frog’s bloodstream. The liver also goes into overdrive, manufacturing vast quantities of glucose, which causes their blood sugar to skyrocket as high as 100x normal levels (a better understanding of how this frog can avoid negative health effects under such conditions could certainly contribute to diabetes research in humans). The urea and glucose create a mixture that acts almost like antifreeze. Once ice crystals begin to form around the blood cells and internal organs, this homemade antifreeze infiltrates, allowing for the retention of water and protecting the frog’s cells from desiccation and explosion. They can maintain this state for up to 8 months.
This brumation strategy earns wood frogs the “northernmost amphibian in the western hemisphere” superlative as they can be found up past Gates of the Arctic National Park in Alaska.
The 2023 Amphibian season has begun! Drive carefully one upcoming rainy nights. Photo credit: Nikki Griffiths.
That’s a wrap on Mr. Freeze and our Super Species! The Amphibian Crossing is now in full swing. If you are going to be driving after sunset along roads that border ponds in the upcoming rains, watch out for migrating frogs and salamanders. Collisions with motor vehicles can decimate local populations rapidly so please slowdown!
This post is the second in our “super salamander (and frog)” series in which we’re exploring some of the unique adaptations exhibited by local amphibians that would seem more appropriate within the confines of a comic book than out and about in our Garden State landscape. Today’s focal species is the spotted salamander (Ambystoma maculatum), our benevolent Poison Ivy. Full disclosure, this topic has nothing to do with plant, though salamanders themselves are not sensitive to the compounds that make humans itchy and have been known to use “leaves of three” as sources of shelter.
For those of you who may be unfamiliar with the DC Comic Universe, Poison Ivy is a villain who often opposes Batman (and occasionally Superman) during her crusade to protect plants and rid the world of environmental destruction. Though her goals may seem in line with ours here at CWF, her methodology differs dramatically and she is often defined as an eco-terrorist. A former botanist, Poison Ivy, AKA Pamela Isley, was poisoned by her professor. Though she survived the experience, the toxins drove her insane and transformed her into a human-plant hybrid. And that is where our connection lies…
If you’ve ever seen an egg mass deposited by a spotted salamander, you may have noticed that the casing often appears green. This is caused by an association with a very particular kind of green algae called Oophilia amblystomatis. The connection between salamanders and algae has been recognized for > 130 years. For most of that time, it was thought that the algae just occurred within the egg. This is a sensible mutualism- it is auspicious to both species involved. Spotted salamander eggs develop in vernal pools. These temporary wetlands may have relatively low concentrations of dissolved oxygen, so the introduction of algae, which can create oxygen through photosynthesis, into eggs can certainly benefit growing larvae. Under experimental conditions where salamander eggs containing algae were cut off from sunlight, growth and development was delayed and resulting individuals were smaller than those exposed to natural circumstances. On the other side, larvae produce CO2 and nitrogenous wastes, which can be used to the advantage of the algae. Studies have shown that Oophilia are most successful in water that has been exposed to spotted salamander eggs, even if they are not within the eggs themselves. Case closed, right?
Developing spotted salamander larva with Oophilia algae. (C) R. Hangarter
Wrong. In 2011, a team of researchers at Dalhousie University in Halifax, Nova Scotia, discovered that the relationship between these two organisms is, literally, skin deep… The algae don’t just infiltrate the salamander’s egg masses. They are also found within the salamander’s tissue cells. This type of connection is called an endosymbiosis- one cell living inside another cell. Coral reefs and their associated algae are the poster children for this phenomenon, but it is not uncommon among invertebrates. Vertebrates, however, tend to have much more active immune systems that are programed to recognize a cell growing within another cell as a health threat. We can be grateful for that, as dangerous pathogens (e.g., malaria), can spread this way. In the case of salamanders and algae, the above-mentioned team discovered that the amphibians were actively suppressing their immune systems to allow for the success of the algae, which indicates that they must continue to benefit from this association. The algae show signs of stress when encapsulated within the body of salamanders; sunlight becomes harder to access, so rather than creating energy through photosynthesis, they switch to the process of fermentation.
The endosymbiotic mutualism between spotted salamanders and green algae is totally unique among vertebrates. No other amphibians, reptiles, mammals, birds, or bony fish are known to support a similar relationship. Research on the mechanisms and the meanings of this “partnership” are ongoing, but scientists are hopeful that the discovery could yield novel techniques for medical advancement.
While spotted salamanders are certainly not hybridizing with their algal associates, in a way, they walk the animal-plant boundary as they incorporate both types of cells within one compact package, therefore making them the amphibious analogs of DC’s Poison Ivy.
Spotted salamander crossed during the 2022 migration.
Our final installment will shift the focus to frogs and, in particular, one that doesn’t mind the late winter chill…
