A Fall Nature Ramble in Florida

November 10, 2014

Nature Notes by Bill Dunson

I have for some time been dissatisfied with being primarily interested in one aspect of natural history such as birds or plants. The variety of fascinating creatures I have encountered this week illustrates the difficulty of restricting your scope of curiosity. I admit the problems of identifying some of the critters and plants can be daunting, but the advent of internet interest groups and simplified identification manuals makes this manageable.

My son, who was visiting from Utah, found this pair of horseshoe crabs (Limulus) in tandem near the southern tip of Little Gasparilla Island. Of course these are not crabs at all but harmless relatives of the spiders/arachnids which are very ancient marine inhabitants. The smaller male has two appendages to hold on to the female until she crawls up on the beach to lay her eggs. The bluish blood has special clotting properties which are quite valuable in medicine, and the eggs are invaluable also in feeding migrating shorebirds. The shed exoskeletons are seen more often than the live animals so it was a special treat to find this pair.

I never cease being amazed by dragonflies and was fascinated by this immature common green darner. This is a very old lineage of insects which is predatory both as aquatic larvae and as the aerial adult. Their behavior is highly visually oriented and the enormous compound eyes made up of 30,000 individual ommatidia are remarkable. The legs are covered with spines which help in holding prey caught and often consumed in flight. Green darners migrate long distances and are capable of complex social interactions. They have become popular objects of observation by those who have mastered birds and want to find new intellectual fields to conquer.

One of the insects most opposite to dragonflies in terms of mobility is the walking stick which is slow moving and camouflaged. You may often find these as mating pairs in Florida and they are sometimes called devil-riders, possibly due to the ability of the large female to squirt toxic terpenes into the eyes of an attacker. So be careful when you examine them!

I spend a lot of time working in our yard and often find interesting critters such as this small greenhouse frog introduced from the Caribbean. It likely immigrated in the root balls of plants brought in by nurseries along with the worm-like Brahminy blind snake. It is quite unusual among amphibians since it lays terrestrial eggs that hatch directly into tiny frogs without an aquatic tadpole stage. The advantage of this in habitats with damp soil but which lack fresh water pools is obvious and allows them to colonize areas unavailable to other frogs.

Two snakes turned up in our yard, a very young corn snake, one of the rat snakes, and a black racer. The corn snake has a series of dark lines on the head, one of which passes through and obscures the dark pupil of the eye. The black racer has a dark area on the upper part of the head, including the dark pupil and a reddish iris. Both of these patterns must make it harder for prey or predators to detect the snake when it is motionless. The corn snake is much more arboreal than the racer and this likely provides some habitat separation which limits competition for food between them.

I was excited to find an adult male Florida box turtle on Palm Island. Although males often have a reddish iris at least some of the year, the reliable way to sex them is by the concave shape of the bottom shell or plastron. The purpose of this obviously is to facilitate mating which must be quite difficult given the rigid shells. Indeed poet Ogden Nash penned the famous lines,

The Turtle
by Ogden Nash

The turtle lives ‘twixt plated decks
Which practically conceal its sex.
I think it clever of the turtle
In such a fix to be so fertile.

While sitting at the computer recently I heard a familiar sound which I knew to be the call of a bald eagle. I rushed outside and looked up at the osprey nest which sits immediately over our house in a tall Norfolk Island pine. There were two eagles sitting in the nest engaged in some bill fencing which soon led to mating. The eagles then left and did not seem interested in taking over the osprey nest which they occasionally try to do. The relationship between these two predators, which compete for fish as food and sometimes for nest sites, reminds me of the uneasy relations between lions and hyenas- in other words not friendly!

So try expanding your horizons and learn a new animal or plant from a taxonomic group with which you are not familiar. It is not as hard as you might think and it will be very rewarding.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

View all posts by Bill Dunson