Roads End Naturalist
Hoping to educate myself and others about nature as I wander and ponder.
Monday, April 1, 2013
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Wednesday, March 27, 2013
Marbled Salamander eggs
Marbled Salamander egg clutch under a log |
Two friends from the Museum, Megan and Melissa, invited me
to tag along with them yesterday, as did some fieldwork for a future workshop.
Megan made a great find as she and Melissa were turning over logs at the edge
of a vernal pool, looking for salamanders – some viable Marbled Salamander
eggs. It seemed really late to us for this species to still have viable eggs (when we looked closely, they could see the well-developed embryo
moving inside the eggs) so she grabbed a couple to photograph.
Marbled Salamanders have an unusual reproductive strategy
compared to many other species in that the eggs are laid in the fall (usually
October and November I think in this area). The female often scrapes out a
little area near or at the edge of a vernal pool. Vernal pools are fascinating and important habitats that may
be dry much of the year and then fill with autumn and winter rains. The key is
they have no fish, which makes them critical habitats for a number of species
of amphibians, invertebrates and other animals. She then will stay with the
eggs for some time (often a month or more) waiting for the water to rise so the
eggs will hatch. If it remains dry for an extended length of time, she may
abandon them and return to her underground burrows in the nearby woods until
the next breeding season. Studies suggest that egg clutches where the female remains
with them until they are covered by water have a higher offspring survival,
perhaps because she helps protect them from predation or getting too dry.
Marbled Salamander eggs |
The 50 or 60 eggs Megan found were under a log at the edge
of a large vernal pool. It was very moist but the standing water was still a
few inches away from the eggs. Embryos develop to the hatching stage within a
couple of weeks after being laid, but do not hatch until covered by rising
water. So these eggs were very well developed. You can see the front legs and
feet, the larval gills, some of the diagnostic lateral spots, and the eyes in
the waiting “larvae”. My salamander reference (Salamanders of the United States
and Canada by James W. Petranka) states, “when covered by water the embryos
become oxygen stressed…this triggers the release (from hatching glands on the
snout) of digestive enzymes that dissolve the egg capsule and allow the embryo
to escape”. Amazing!
A closer look |
We put a couple of eggs in some water in a bug box so I
could photograph them. Megan called Jeff Beane, a herpetologist at the Museum,
and told him about the find. He said he did not recall seeing any viable eggs
this late in the spring so he wanted to document the location. We walked down into
the woods to show him, photographed the eggs and then walked back to the car.
In those 40 minutes or so, the two eggs had hatched. The reference said it usually
takes a few hours to a couple of days after flooding for the eggs to hatch.
Guess these guys had waited long enough. The last picture is one of a larva
from last year that I pulled from another pool. It was much older and larger
than the ones from yesterday.
Large Marbled Salamander larva |
Monday, March 25, 2013
Hollow log Bluebird house
This is in response to a friend’s request for information on a natural-looking bluebird house. I have made several of these out of appropriate sized hollow tree trunks (just compare to a commercial bird house for approximate dimensions). After finding and cutting the hollow log into reasonable lengths, I use a large screwdriver to scrape out the interior (if needed) so as to have a decent cavity. The entrance hole is made with a one-inch diameter drill bit. I usually rough up the edges a bit to enlarge it slightly and to make it look more natural. The top and bottom of the house are made with rough lumber and pre-drill attached with wood screws. I overlap the roof all the way around to provide some shelter from rain.
The mounting bracket is made with a one-inch strip of
aluminum (Lowes, etc. carry all of these pieces) cut to a length that allows it
to be doubled over for inserting into the mounting pole. Drill two holes for
the bracket to attach it to the back of the house. I am careful to use as short
wood screws so there is not a sharp screw tip inside the nest cavity that might
injure the birds. Then bend the bracket so the free end slides down into the
mounting pole. I usually compress
the top of the mounting pole with a hammer so the bracket slides easily down
into the narrow slit. One and a quarter-inch diameter electrical conduit is
used for the long top mounting pole (I usually use 10 ft lengths and cut it in
half) and it slides over a shorter, smaller diameter rod or piece of re-bar
driven into the ground with a sledgehammer. Strike the conduit with a hammer a
foot or so from the bottom to create a dent that will act as a stop when it
hits the top of the ground pole as you slide the conduit down over it. The
location of the dent allows you to adjust the height of the unit as
needed. The boxes tend to last a
few years depending on the durability of the hollow log. I rarely clean out
these boxes but they are used many times (after all, no one is cleaning out the
natural cavities out there and some studies of nest boxes have hinted that
parasites of nest parasites increase in number, thereby reducing nest parasite
populations, if next boxes are not cleaned out frequently). Before setting in the box, I often finish the pole system off by slipping a length of 4 inch diameter PVC pipe over the mounting poles. Some say this may help deter snakes from climbing into the nest box. If I use it I always put sticks or grass or other debris down into the top of the PVC to prevent any birds from getting stuck in that pipe.
All of this effort is to provide a natural-looking cavity
for the birds and a photographic backdrop for me. I usually put a pop-up blind
near the nest box and allow the birds to get used to it empty before I start
entering and taking pictures. Below are a couple of images from one such nest
box in late afternoon light.
Saturday, March 23, 2013
Crawling on your back...doing the Grub
June Beetle Grub |
Green June Beetle grub crawling on its back |
Green June Beetle larvae have stiff abdominal and thoracic bristles, short stubby legs,
and wide bodies. When I left this grub alone for a few seconds it started crawling on
its back by undulating and using its dorsal bristles and ridges to gain traction. I was impressed at how quickly it moved as it covered several inches in a few seconds. Seems like an odd locomotion strategy but all the references I looked at said the legs are too small to be useful for crawling (especially relative to other species of white grubs).
Green June Beetle grubs overwinter as larvae and may
become active on warm nights throughout the winter. Their burrows can be several inches deep (the depth depending on temperature and soil conditions). Their primary food is dead and
decaying plant material. They resume feeding once the ground warms in the spring and
then pupate in late May or early June. The adults begin emerging a few
weeks later. I'll be on the lookout for the adults in a couple of months and try to learn more about their behavior.
Oh, I almost forgot to mention that I have a long history with grubs of various sorts. My most memorable encounter was in the Amazon years ago, while leading a teacher workshop with the NC Museum of Natural Sciences (where I worked for 24 years as an educator and naturalist). There were two Peruvian teachers with our group and one morning, while bird-watching, one of them got excited when he heard something in a log next to the trail. He ran back to the village and returned with a machete which he expertly used to chop out several very large grubs (as I recall they were well over 3 inches in length, compared to almost two inches for the Green June Beetle grub here). He had hard them chewing in the log and realized what a treat he had found. As any polite person would do, he offered the first bite of one to the three leaders of the group (turns out the grubs were considered delicacies by the locals). Well, being the youngest of the three, I naturally got the tail end of the grub as my share...let's just say I didn't chew much. Later that evening the remaining grubs were roasted and served as a great protein snack. I definitely recommend the roasted grubs (which were somewhat nutty in flavor) over the raw ones, both in taste and texture:)
Oh, I almost forgot to mention that I have a long history with grubs of various sorts. My most memorable encounter was in the Amazon years ago, while leading a teacher workshop with the NC Museum of Natural Sciences (where I worked for 24 years as an educator and naturalist). There were two Peruvian teachers with our group and one morning, while bird-watching, one of them got excited when he heard something in a log next to the trail. He ran back to the village and returned with a machete which he expertly used to chop out several very large grubs (as I recall they were well over 3 inches in length, compared to almost two inches for the Green June Beetle grub here). He had hard them chewing in the log and realized what a treat he had found. As any polite person would do, he offered the first bite of one to the three leaders of the group (turns out the grubs were considered delicacies by the locals). Well, being the youngest of the three, I naturally got the tail end of the grub as my share...let's just say I didn't chew much. Later that evening the remaining grubs were roasted and served as a great protein snack. I definitely recommend the roasted grubs (which were somewhat nutty in flavor) over the raw ones, both in taste and texture:)
Friday, March 22, 2013
Shed in the shed
Spider shed |
Chilicerae on shed |
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