Category Archives: Fish, Frogs

On Cape Cod It’s Always Shark Week

Great white shark, South Africa (photo from Wikimedia Commons)

30 July 2023

This may be the last day of Shark Week on the Discovery Channel but on Cape Cod it runs all year. A new study published this week in Marine Ecology Progress Series tagged and counted great white sharks (Carcharodon carcharias) off the coast of Cape Cod, Massachusetts and found that 800 individuals visited the area from 2015 to 2018. That means Cape Cod may have the highest density of white sharks in the world.

Fortunately all the sharks weren’t there at the same time. As lead author Megan Winton of the Atlantic White Shark Conservancy (AWSC) explains, great white sharks are highly migratory. Their population peaks on the Cape from July to November when the water is warm, as shown in this screenshot from AWSC’s logbook for 2022. Individual sharks spend a few hours or a few weeks in the area. (Click here to see AWSC’s shark data and download their shark app.)

AWSC white shark logbook by month for 2022 (screenshot from AWSC)

The sharks are attracted to the Cape by the abundance seals, one of their favorite foods. A Google Haul Out survey of southeastern Massachusetts estimated maximum counts of gray seals at 30,000 to 50,000 animals in 2012 to 2015. Harbor seals arrive in the fall and add to the seal population. No wonder sharks show up. Gray seals provide a lot of meat, weighing as much as 800 pounds.

Gray seals at Nantucket NWR (photo from Wikimedia Commons)
Gray seals at a haul out in Nantucket NWR (photo from Wikimedia Commons)

During our recent trip to Cape Cod I saw lots of seals at Chatham Fish Pier. Several swam by the fishing boats but the vast majority were hauled out on a sand bar across the harbor. See that lumpy line of gray blobs? Those are gray seals.

Gray seals line the edge of the sand bar across from Chatham Fish Pier on Cape Cod, 12 July 2023 (photo by Richard St. John)
Gray seals line the edge of the sand bar across from Chatham Fish Pier on Cape Cod, 12 July 2023 (photo by Richard St. John)

While on the Cape I didn’t see any sharks but I did see a No Swimming shark sign at Race Point. I was looking for birds and, as it turns out, diving seabirds give the hint that a shark may be nearby. Both feed on schools of fish, the birds from above, the sharks from below.

The abundance of sharks and seals in Cape Cod’s waters is an environmental success story. Gray seals were almost extinct in U.S. waters by the mid 20th century because of bounty hunting in Maine and Massachusetts from the late 1800s to 1962. The seal population began to recover, slowly, when the bounties ended. Sharks made a comeback because of the seals.

Learn more in this ABC News interview with lead author Megan Winton of Atlantic White Shark Conservancy.

video embedded from ABC News on YouTube

p.s. Well, technically, it’s only Shark Week for 5 months on Cape Cod — mostly from July to November.

(photos from Wikimedia Commons and by Richard St. John, graph is a screenshot of AWSC’ logbook website; click on the links to see the originals)

Miniature Flying Dragons

Artistic reconstruction of ancient flying lizard, Weigeltisaurus jaekeli (image from Wikimedia Commons)

28 October 2022

Back in the Late Permian, 258 to 252 million years ago, there was a family of gliding lizards called Weigeltisauridae whose fossils have been found in Germany, Britain, Russia and Madagascar. Europeans drew them as dragons.

Winged dragon on the ground, illustration in: Athanasius Kircher’s Mundus Subterraneus via Wikimedia Commons

Today there are still gliding lizards on Earth but they are smaller and live in Asian jungles. Dracos can glide 100+ feet from tree to tree by extending their long skin-covered ribs.

Draco taeniopterus flying and Draco volans skeleton (image from Wikimedia Commons)

Watch one fly to escape a dominant male in this BBC Planet Earth II clip.

Learn about Draco dussumieri of Southern India in this video from Roundglass.

Where do Dracos live? Click on the map caption to see a larger view.

(photos, maps, a video and illustrations from Wikimedia Commons; click on the captions to see the originals. videos also embedded from YouTube)

The Most Teeth in North America?

Sperm whale skeleton showing teeth (photo from Wikimedia Commons)

19 September 2022

Adult humans typically have 32 teeth after our wisdom teeth come in at age 12-14, but our count is low compared to other animals.

7-year-old smile with missing tooth (photo from Wikimedia Commons)

Which animal in North America has the most teeth?

The Virginia opossum (Didelphis virginiana) is a contender with 50 teeth in his small mouth. He shows them when he feels threatened.

Opossum showing teeth (photo from Wikimedia Commons)

Some say that sharks have the most teeth but as far as I can tell their tooth count, often lower than 100, is not as remarkable as their tooth replacement. For instance, young lemon sharks replace all their teeth every 7-8 days so that in their lifetimes “the lemon shark Negaprion brevirostris, may produce 20,000 teeth in its first 25 years, and may live as long as 50 years.

The winner of the most-teeth contest are land and sea snails which usually have between 10-15,000 teeth, though some may have up to 25,000. This includes snails in the ocean off the North American coasts.

Studies of the European garden snail (Cornu aspersum), an alien in North America, indicate it has 14,000 teeth. Take a look at his toothy mouth under a microscope and find out why snails have so many teeth at NMH.org: Microscopic look at snail jaws.

European garden snail (photo from Wikimedia Commons)

Amazingly, the most abundantly land snail found in Pennsylvania, Zonitoides arboreus, has no teeth at all!

Quick gloss snail, Zonitoides arboreus, Edgewater, Maryland (photo from Wikimedia Commons)

(photos from Wikimedia Commons; click on the captions to see the originals)

Scallops on the Move

Atlantic bay scallop shell (photo from Wikimedia Commons)

7 August 2022

Scallops travel by opening and closing their shells but the direction they move seems counterintuitive. They don’t lead with their hinges. Instead the open edge goes first as they use their eyes to guide themselves.

Scallops’ eyes look like bright beads at the shells’ front edge.

Slightly open live Atlantic bay scallop; eyes look like bright beads (photo from Wikimedia Commons)

Watch scallops on the move in this Twitter movie.

(photos from Wikimedia Commons; click on the captions to see the originals)

Flat or Spiky, Always Toxic

Puffed up porcupinefish (photo from Wikimedia Commons)

11 July 2022

This spiky ball, a pufferfish, is so toxic that if eaten it can kill 30 adult humans.

There are more than 260 species of pufferfish in two families, almost all of which are toxic: Diodontidae and Tetraodontidae. The spiky ones are aptly called porcupinefish.

They don’t swim fast so their main defense is to blow up into an unappetizing ball. When fully extended their buoyancy changes and they involuntarily roll onto their backs, exposing their white bellies. In this position they can still swim with tiny fins.

How do pufferfish blow themselves up? Why are they toxic? Who eats them? This video explains it all.

And though they are spiky, they somehow they manage to look cute.

(photo from Wikimedia Commons; click on the captions to see the originals)

Lightning and Fish

Lighting strikes as the USS Abraham Lincoln transits the Strait of Malacca (photo from Wikimedia Commons)

6 July 2022

When a thunderstorm approaches at the beach or a swimming pool, the lifeguards tell everyone to get out of the water. Lightning often strikes water and anyone in it can be electrocuted.

Fish live in water so why don’t they die from lightning? The National Weather Service explains:

Before a lightning strike, a charge builds up along the water’s surface. When lightning strikes, most of electrical discharge occurs near the water’s surface. Most fish swim below the surface and are unaffected.

National Weather Service: Lightning and Fish

This NWS animation shows the positive charge building on the surface and the negatively charged lightning strike spreading horizontally. Fish swim below it all.

Humans swim on the water’s surface where lightning has its greatest effect. In addition, lightning is a hazard in open outdoor spaces like beaches.

West Beach Galveston, 1973 (photo from Wikimedia Commons)

Interestingly in the US, the most dangerous activity during lightning is fishing; beaches are second. We thought golf was the worst but it is far down on the list.

US lightning death statistics by activity, 2010-2021 (table from National Weather Service, Paducah, KY)

During a thunderstorm the fish are safer than the fisherman.

(photos and animations from Wikimedia Commons; click on the captions to see the originals)

Thriving Near Mountaintop Removal

Green salamander (photo from Wikimedia Commons)

13 June 2022

Some salamanders are easy to find, some are rarely seen, and some, like the green salamander, are so rare that they’re listed as Near Threatened. It was quite a surprise to find anything, let alone green salamanders, thriving in the remnants of mountaintop removal in Virginia in 2016.

The green salamander (Aneides aeneus), native from Alabama to Pennsylvania, is a habitat specialist that lives in the dark furrows of naturally moist rock outcrops on cliffs in the Alleghenies and Cumberland Plateau.

Green salamander on rock outcrop (photo from Wikimedia Commons)

His favored habitat is usually close to trees — he climbs them.

Rock outcrop in Breaks Interstate Park, KY-VA (photo from Wikimedia Commons)

In April 2016 when Dr. Wally Smith of University of Virginia Wise County decided to look for salamanders at an old mountaintop removal site, he didn’t expect to find anything in the half-acre remnant of rocks and trees left by the mining company. He was stunned and overjoyed to find a green salamander.

Working with Kevin Hamed of Virginia Highlands Community College, Smith surveyed more mountaintop removal sites. There’s a lot from choose from in Wise County, Virginia.

Satellite photo of mountaintop removal in Wise County Virginia at the Kentucky border (photo from Virginia Division of Mined Land Reclamation via virginiaplaces.org)

They found that …

Unsurprisingly, hillsides and rock walls that had been directly carved up or deforested didn’t hold any salamanders. But around 70 percent of the surviving natural outcrops did—often in surprisingly healthy numbers. As long as the old crevasses and tree-cover were present, the species showed up, regardless of the racket and disturbance nearby. “The salamanders in these pockets seem to be doing pretty well,” Smith said. “They’re abundant, they’re reproducing, which are signs that the populations are still hanging on.”

Gizmodo: Rare Appalachian salamanders are reclaiming abandoned Coal Mines

The discovery led to more questions so Smith and Hamed expanded their search and, with the help of locals and landowners, found 70 locations with salamanders including …

… a motherload of salamanders in the municipal park of a local city. “Usually if you’re lucky, you find one or two a day. There, we were finding 70 to 100 per hour,” said Smith.

Gizmodo: Rare Appalachian salamanders are reclaiming abandoned Coal Mines

This photo of Kayford Mountain, WV gives you an idea of the remnant pockets the mining companies leave behind.

Mountaintop removal at Kayford, WV with remnant stand of trees (photo by Rana Xavier via Flickr Creative Commons license)

How did green salamanders get to these sites? Is each site a remnant “island” population or do the groups interchange with populations elsewhere? The study continues.

Meanwhile it’s a miracle to find them at all.

Read more about the salamanders at mountaintop removal sites in Gizmodo: Rare Appalachian salamanders are reclaiming abandoned Coal Mines.

Learn more about mountaintop removal before-and-after at Appalachian Voices.

(photos from Wikimedia Commons, Virginia Division of Mined Land Reclamation and Rana Xavier via Flickr)

April Fooling Frogs

Wood frog close up (photo from Wikimedia Commons)

2 April 2022

Have you heard ducks quacking deep in the woods lately? The sound comes from a soggy wooded place or puddle or tiny pond and there is no duck in sight.

Nature is playing an April Fool’s joke. Those aren’t ducks or chickens. Those are male wood frogs calling to attract females. If you could see what they were doing you’d find …

Wood frogs (Rana sylvatica) gather together in large leks to mate. In these leks, males are much more common than females, typically outnumbering females by at least two to one. The males arrive first, and begin calling and wrestling with each other. As female wood frogs arrive at the ponds, they swim toward the center of the lek. Multiple males grab them, clinging to each female until one male wins out. This particular mating behavior, in which the male clings to the female, is known as amplexus. The females will typically each lay a single egg clutch consisting of about 400-1,200 eggs.

Description of Wood Frogs from Mister Toad website by Michael F Benard @BenardMF

Wood frogs are some of the earliest frogs to appear in the spring so don’t wait. Get outdoors soon before they’re done mating.

(photo from Wikimedia Commons, video by Gregory Bulte)

Woodcocks and Peepers

  • Sunset at North Park's Upper Field, 16 March 2022, 7:32pm

20 March 2022

Last Wednesday evening, 16 March, eight of us waited at dusk near the Viewing Platform in North Park’s Upper Field for the woodcocks’ sky dance to begin.

The sun set at 7:27pm, the sky flamed and dimmed. It was barely glowing twenty minutes later when we heard the first “peent.”

On dry Spring nights male American woodcocks (Scolopax minor) gather in shrubby fields to mate with females who intend to nest there. Within the hour after sunset or in the hour before sunrise, they let the ladies know they’re available by stomping around in the dark calling “peent, peent, peent.” After some peenting each male flings himself into the sky climbing hundreds of feet before circling back down. While ascending his wings make a twittering sound, while descending his wings chirp. You can tell what he’s doing by listening in the dark. He lands where he started and does it again.

American woodcock (photo from Wikimedia Commons)

Listen to a complete cycle of peenting + whistling and chirping wings.

American woodcock display, Fauquier County, Virginia from Xeno Canto

On Wednesday the moon was almost full and the woodcocks were very active. We heard at least six of them!

Waxing moon over Upper Field, North Park, 16 March 2022, 8:01p (photo by Kate St. John)

The spring peepers at Eagles Nest parking area were active, too.

Spring peeper calling in the Ozarks (photo by Justin Meissen via Wikimedia Commons)
Spring peeper calling in the Ozarks (photo by Justin Meissen via Wikimedia Commons)
Spring peepers at North Park, 16 March 2022 (recorded by Kate St. John)

Woodcocks will continue their sky dance in April and early May but if you want two audio treats at once, go out in March by the light of the moon.

(sunset and moon photos + sound of spring peepers by Kate St. John. Woodcock and peeper photos from Wikimedia Commons. Woodcock audio from Xeno Canto)

It’s a “Newdybrank”

Gas flame nudibranch (photo from Wikimedia Commons)

16 March 2022

What looks like a glowing pincushion (above) or piece of plastic in the tweet below is an animal called a nudibranch. It’s not pronounced the way it’s spelled. The “ch” is a “k.” This is a “NEW-dih-brank.”

Nudibranchs are sea slugs whose name means “naked gills” though some of them have no gills at all. From a video at DeepMarineScenes I learned that nudibranchs are …

  • 3000+ species of sea slugs similar to snails but without any shells inside or out,
  • Found from the poles to the tropics, most often in shallow tropical waters,
  • Carnivores that eat sponges, corals, anemones, etc.
  • Range in size from 1/4 inch to 1 foot long,
  • Use smell and feel to get around. Their eyes sense only light and dark.
  • Brightly colored from the toxic things they eat.
  • Toxic themselves. Their color warns off predators.
  • Their only real predators are other nudibranchs. Yow!

Here are a few more species.

Red nudibranch (photo from Wikimedia Commons)
Nudibranch, Nembrotha lineolata (photo from Wikimedia Commons)
Nudibranch, Nembrotha kubaryana (photo from Wikimedia Commons)

Take a look at their lifestyle in a video from PBS’s KQED Deep Look.

For lots and lots of information about nudibranchs see this 5+ minute video from DeepMarineScenes: Facts: The Nudibranch.

(photos from Wikimedia Commons; click on the captions to see the originals; video embedded from KQEDDeepLook)