21 October 2022
No matter where they live beavers (Castor canadensis) must gnaw wood every day to wear down their constantly growing front teeth. In captivity they are given wood to keep their teeth healthy.
A beaver in rehab doesn’t have to make a dam but it’s obviously an instinct that’s hard to deny. He builds a dam at the doorway.
Busy as a beaver!
(photo from Wikimedia Commons, embedded video from YouTube)
16 October 2022
Dolphins have specialized skin for their underwater lives. The outer layer (epidermis) feels rubbery and is 15 to 20 times thicker than our own. It stays smooth because:
Dolphin skin constantly flakes and peels as new skin cells replace old cells. A bottlenose dolphin’s outermost skin layer may be replaced every 2 hours. This sloughing rate is 9 times faster than in humans. This turnover rate ensures a smooth body surface and probably helps increase swimming efficiency by reducing drag (resistance to movement).
— Seaworld.org: Bottlenose dolphin characteristics
Dolphins will even take turns to rub their bodies on corals and sponges, an activity that probably feels good. (video: Why Taking Turns Is Good for Dolphin Skin)
We know these things about dolphins because some have a close association with humans. Veterinarians and trainers take an active interest in the welfare of animals in their care.
Dolphin veterinarians are especially concerned that as dolphins age, their heart health may suffer. This includes the dolphins in the U.S. Navy’s Marine Mammal Program in San Diego.
Last year the Navy asked for proposals to place heart monitors on their aging dolphins to unobtrusively monitor them as they move about in the ocean. There are many challenges to doing so including the dolphins’ skin. Because the skin turns over every two hours nothing can stick to it for long. I wouldn’t know about their skin if I hadn’t heard about the heart monitors.
The vast majority of us rarely if ever seen dolphins in the wild and know very little about their lives. We are mesmerized when we see them this close.
It’s hard not to love them.
(photos from Wikimedia Commons and from Royal Society Publishing; click on the captions to see the originals)
10 October 2022
The season has changed and the woods in Schenley Park look different than they did a month ago. The trees are putting on fall color and deer are providing more evidence of their overpopulation in the park.
With the growing season over there is less greenery for deer to eat and there are fewer places to browse because they have already denuded many areas.
What is left has been eaten down to nubs, just visible above the unpalatable invasive plants. Below, goutweed nearly hides the tops of what used to be jewelweed while pokeweed was browsed to tiny leaves and bare stems.
As the greenery disappears deer eat tree saplings and small branches. In cases of deer overpopulation, such as Schenley Park, the young trees are foraged down to bonsai.
Schenley no longer has enough food for deer so at night they walk into neighborhoods and browse in backyards. This is happening across the city and has prompted some residents to consider a Deer Management Plan for Pittsburgh. KDKA’s Andy Sheen reports: Some Pittsburgh residents say it’s time to get deer population under control. Click on the link or the screenshot below.
(photos by Kate St. John + screenshot from KDKA)
7 October 2022
Giant anteaters (Myrmecophaga tridactyla) are related to sloths and are native to Central and South America. True to their name they eat ants and insects and their bodies are formed for that lifestyle, including a long snout and tongue and powerful claws for digging out insects.
Here are six ways of looking at an anteater.
Giant anteater mother carrying baby on her back
Learn more about giant anteaters at Wikipedia.
(photos from Wikimedia Commons; click on the captions to see the originals)
5 October 2022
Some dogs are bred to herd sheep and the instinct is so deep that they try to herd at every opportunity.
However, training helps. So does experience, as shown in this tweet from @SlenderSherbet.
When your lack of sheepdog experience is cruelly exposed on your first day. pic.twitter.com/5lUozof6dk
— Paul Bronks (@SlenderSherbet) September 7, 2022
(photo from Wikimedia Commons, embedded tweet from @SlenderSherbet)
3 October 2022
The hardest thing to notice in Nature is the date of an absence. When did the last junco leave in the spring? When did the last groundhog go into hibernation?
Right now eastern chipmunks (Tamias striatus) are busy gathering nuts to store in their underground burrows for the winter. As the season changes and temperatures drop they will disappear into their burrows to enter torpor, sleeping off and on through the winter.
The warm winters of climate change can fool them into not entering torpor but the result is deadly. Only 10% survive. Find out why in this vintage blog:
Meanwhile I will hope our chipmunks disappear and will try to figure when they do it.
Here’s how I notice an absence: I write down every day when I do see them and then scan my notes for days when I’ve not logged them anymore.
(photo from Wikimedia Commons; click on the link to see the original)
29 September 2022
In western Pennsylvania, where we have a high deer population, gardeners have learned from experience that white-tailed deer will eat some plants and not others. They heavily browse their favorites to the point of killing them but leave others untouched, even plants in the same genus.
Viburnum is a case in point. Gardening advice at Rutgers University’s Landscape Plants Rated by Deer Resistance indicates that arrowwood viburnum (Viburnum dentatum) is deer resistant. Pictured at top, these shrubs are healthy in Schenley Park where the deer population is more than 100 per square mile.
Deer also don’t like the Japanese snowball (Viburnum plicatum) which thrives as an invasive in Frick Park, shown below.
But they love our native hobblebush (Viburnum lantanoides) and consume it to local extinction.
Read about hobblebush in this vintage article.
When it comes to viburnum, deer are picky eaters.
(photos by Kate St. John)
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.
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.
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.
Amazingly, the most abundantly land snail found in Pennsylvania, Zonitoides arboreus, has no teeth at all!
(photos from Wikimedia Commons; click on the captions to see the originals)
17 September 2022
In Schenley and Frick Parks you can look straight through the forest if you duck your head below four feet high. In Schenley Park the ground is often bare and most plants in that four-foot zone are gone. But one flower, wingstem (Verbesina alternifolia), is doing just fine in the city parks.
The absence of cover from the ground to 4 – 5 feet is called a browseline (below) and is evidence of an overpopulation of white-tailed deer.
According to this KDKA report, the deer population in Schenley Park is estimated at 80-120 per acre, which roughly equates to 57-86 deer per square mile. A 2010 deer study for City Parks found that the parks can support 7-8 deer per square mile, but with 8 to 11 times that number living in Schenley any plant still growing there is definitely something deer don’t eat.
So why don’t deer eat wingstem?
The leaves are bitter!
Find out more about wingstem at Illinois wildflowers.
(photos by Kate St. John)
15 September 2022
At this time of year the birds are not singing but you often hear a “chip” note in the woods. It’s not the sound of a bird but instead a chipmunk, making the noise that puts “chip” in his name.
“Chip” is warning sound that means Danger From the Ground. Chip Chip Chip Chip, the speaker is warning of a ground-based predator — a cat, raccoon, snake, etc.
Chipmunks “chip” at different speeds, even during the same chipping session, as seen in the 4.5 minute video below. The tonal quality and variable speed give us a hint that it’s a chipmunk speaking, not a bird.
The second most common chipmunk sound is another warning.
“Tock” means Danger From The Air — a clue that birders should look for a raptor. Tock Tock Tock Tock. Listen and learn in this vintage article.
p.s. This article explains the chipmunk’s vocalizations: What Sounds Does A Chipmunk Make?
(photo by Chuck Tague)