Q: Why do turtles spread their legs and feet out when they rest on logs?
A Red-bellied Turtle basks in Bird Rookery Swamp.
A: Turtles are cold-blooded animals, so they cannot control their body temperature internally. The only way they have to raise their body temperature is to bask to absorb warmth and vital UV rays. While heat is radiated to their bodies from their shells, they often stretch out their legs to collect additional heat.
Usually, their feet completely widen out at the same time to increase the surface area even more. They are able to engage in thermoregulation and their metabolism functions become elevated. As a result, the efficiency of their immune and digestive systems increases. Another benefit is that they absorb important UVB rays in sunlight. UVB rays become metabolized into vitamin D3 which is necessary to process calcium.
Q: What causes the small brown and yellow patches on healthy plant leaves?
An Alligator Flag leaf by the Bird Rookery Swamp boardwalk protects itself from further damage by isolating an invasive pathogen.
A:
It’s often apoptosis, a term that comes from plant kingdom where the Greek apoptosis originally meant the loss of petals of leaves. Now, it can refer to both the plant and animal kingdoms and is also called Programmed Cell Death (PCD).
Cells in plants and animals can self-destruct when they are no longer needed or if they are damaged. For plants, this achieves and maintains stability within the internal environment when it is dealing with external changes.
Natural PCD (not caused by external factors) includes the timely death of petals after fertilization and the senescence of leaves. Host-controlled PCD is also a means of resistance to pathogens. Cells challenged by pathogens initiate a hypersensitive response, which is a rapid PCD process that is activated in order to inhibit the spread of invading pathogen.
PCD in plants has a number of molecular similarities to animal apoptosis, but it also has differences. The most obvious is the lack of an immune system to remove the pieces of the dead cell.
Greatly simplified, instead of an immune response, an enzyme is activated that destroys the central vacuole (a bubble-like cavity) in the plant cell, which is followed by disintegration of the rest of the cell. This creates a protective, dead “envelope” around the pathogen to limit its spread. This is what may appear on some leaves as a yellow and brown blotch.
Some examples of apoptosis in the animal kingdom include the resorption of the tadpole tail at the time of its metamorphosis into a frog, the removal of tissue between fingers and toes of the fetus as it develops, the elimination of T cells that might otherwise mount an autoimmune attack on the body, and during the pupal stage of insects that undergo a complete metamorphosis, the death of most of the cells of the larva which provide nutrients for the development of the adult structures.
Q: If raccoons are out in the daytime, are they dangerous?
Raccoons are destructive little creatures whose only saving grace is that they can be cute. They are wild animals and should be treated as such. Photo and caption by Dick Brewer.
A: Raccoons are often seen during the day, causing some people to ask, “I thought raccoons here only active at night and the only ones out in the day were rabid. Is it safe here?”
Raccoons are wild animals, and like all wild animals, from small snakes to big bears, they should be regarded with caution and treated with respect. But they are not inherently dangerous. It’s all about predator avoidance.
Raccoons, like all animals, want to survive. They want to get food rather than to be food, so they must minimize the chances of being killed by predators while foraging.
In the more peopled areas, raccoons tend to be more active at night because that’s when they encounter fewer predators and obstacles to getting food such as people, cars, big dogs, and more.
In Florida’s wild areas, their most dangerous predators — alligators, panthers, and bobcats — are most active and most efficient at night. In those habitats, the best chance for a raccoon to survive is to hunt during the day.
This month’s Q & A post by CREW volunteer naturalist Dick Brewer
Q: How can snakes climb up trees?
A: Snakes use “concertina locomotion” to climb trees – the act of gripping with some parts of the body while pulling or pushing with other parts of the body in the general direction of movement. Ripples of muscle travel along the snake’s length while the spaces in between
inch forward.
Concertina locomotion is very irregular and appears to be quite strenuous. So, it takes snakes much longer to climb a tree than they could move on the ground or in the water.
This push/pull motion is made possible by scales that are keeled, or ridged. Think of the keel on the bottom of a boat. Unlike smooth scales, keeled scales have raised ridges on the center of each scale which enables the snake to get a grip on rough surfaces, much like a tire with a good tread grips the road better than a bald tire.
Snakes cannot stick to smooth walls the way insects and lizards often do; the snake must have something for the keel to rest on in order to push up. So working in concert with the body muscles, the keeled scales lodged in bark crevices help the snake push against the bark on the tree and inch upward. And yes, sometimes snakes do lose their grip and fall out of a tree.
All snakes either have smooth or keeled scales, and one way to distinguish is that smooth scales typically reflect light, making the color pattern of these snakes shiny, glossy, or iridescent, whereas keeled scales tend to make snakes appear dull and non-reflective because of the raised ridge. Because snakes climb with their bellies to the tree trunk, the scales on their undersides of some snakes may be keeled while the scales on the topside may not be.
The Yellow Rat Snake is the best tree climbing snake in Florida. (Photo by Dick Brewer)
This week we begin a monthly Q & A post about various natural history topics written by CREW volunteer naturalist, Dick Brewer. This month he tackles a frequently asked question from Bird Rookery Swamp visitors.
Q: What made the large platform up in the tree, and does anything live in it? (This can be seen at the 0.5 mile marker at Bird Rookery Swamp)
A large Witches’ Broom growing on a cypress in Bird Rookery Swamp above the 0.5 mile post. (Photo by Dick Brewer)
A: It’s called a Witches’ Broom. It’s a dense cluster of twigs/needles growing from a central source, sort of resembling a broom. It is a symptom of stress found in woody plants, mainly trees but also shrubs. The stress results in a deformed mass of twigs and branches which often appear broom-like. It can be small or up to several feet across.
The term Witches’ Broom dates to medieval Europe when people looked up into trees and saw what looked like a mat of twigs woven together and believed that witches placed them high in the trees and even rested on them. As brooms were once fashioned together from bundles of twigs, and since witches were presumed to be responsible for anything unusual, the abnormalities gave rise to the common name.
Factors which may cause Witches’ Brooms include infestations of mites or aphids or parasitic plants like mistletoe, genetic mutations, infection by fungi or phytoplasmas (wall-less single celled organisms with unorganized nuclei), or adverse environmental conditions that kill the terminal bud of the shoots.
Those caused by genetic mutation may be stable, so people have been able to propagate them vegetatively as dwarf cultivars. Regardless of the cause, each one is the only one of its kind in the world and is genetically unique.
In Florida, many of the Witches’ Brooms are a result of a fungal infection from Sphaeropsis tumefaciens (reference: http://mrec.ifas.ufl.edu/jos/Sphaeropsis.htm). Plants in Florida known to be affected by this disease are oleander, holly, bottlebrush, citrus, crepe myrtle, ligustrum, and even Brazilian pepper.
On some of these plants, the symptoms produced are a knotty gall rather than the mass of twigs known as Witches’ Broom. Sometimes, Witches’ Broom can be caused when the tree is stressed from a branch that broke off by accident or was poorly pruned by a person.
Witches’ Broom can last for several months to several years, and while it may be unsightly to some people, it really poses no serious threat to a healthy tree or shrub.
Witches’ Brooms can be ecologically important. They tend to be inhabited by a wide variety of organisms apart from the causative one. Some species of moths rely on them exclusively for food and shelter for their larvae, and larger animals including many arboreal rodents such as flying squirrels may nest in them.
