A study of hibernation sites of snakes in Buenos Aires province
1. A study of hibernation sites of
snakes in Buenos Aires
province, Argentina
Camila Kass
Faculty of Natural Sciences and Museum of the
National University of La Plata, Argentina.
FCNyM-UNLP
3. Hibernation is a direct response to lower body temperature and to
changes in the availability of food.
In this period, metabolic activity ceases almost entirely and
physiological processes are reduced to a minimum.
Body temperature will be determined by
the shelter during the winter.
Therefore, species must select sites where
temperature and humidity are constant
to live through the winter.
4. Lizards can use their limbs to dig in the soil and make their burrows.
However, snakes should use existing holes in the ground, on tree
trunks, or hide under stones or other objects within abandoned
nest.
5. The use of anthills and termite mounds as hibernation sites
has been documented in several countries. Nevertheless,
there is scarce information about the use of them as
hibernation sites in Argentina.
6. Previous studies have shown the existence of incubatory inquilinism
between ants of genus Acromyrmex and different species of snakes and
lizards.
Therefore, anthills chosen for inspection where the ones from this genus.
The nests of fungus-growing ants are usually
large, with domes of earth and plant material
that protrude several inches from the floor, with
chambers of variable size.
It is believed that some snakes may have
chemical and / or morphological adaptations
that ease this commensalism with ants.
7. Hypothesis and objectives
As Acromyrmex anthills have already been recorded as oviposition sites,
the hypothesis of this project states that hibernation also takes
place inside them.
To test this hypothesis, the aim of this project is to obtain records from
their inspection through the use of a videoendoscope.
9. Study area
The study area selected was in the Natural Reserve “El Destino", Punta
Indio (Provincia de Buenos Aires, Argentina).
10. In 2010, field trips were conducted to recognize and find anthills from
Acromyrmex. After that, the specific site chosen was a pasture, an area
of approximately 8 hectares, where the highest density of anthills was found.
In 2011, samples were taken weekly during the winter period of June-
September, when 25 anthills were found.
Having identified the anthills, they were randomly selected for internal
inspection, obtaining a random number with a scientific calculator. The aim
of this was that each mound, regardless of size, have the same probability of
being chosen.
11. Each anthill was georeferenced, numbered and photographed before being
examined.
In addition, more data was collected for further analysis (the length of the major
and minor axes with a meter and temperature flex in three different points of the
nest to obtain an average temperature of each anthill).
Only 10 anthills were randomly selected and examined.
12. The tool used was a with a videoendoscope, an endoscope fitted with a
video camera at its front. The videoendoscope was plugged to a notebook
through a USB port and videos were recorded with Ulead Video Studio SE
software in *.AVI format.
Also a garden shovel was used to dig each anthill after the video inspection.
14. The results of internal inspections of the ten chosen Acromyrmex anthills
show the absence of hibernating reptiles inside them.
We consider different problems in the use of the endoscope that emerged
during the study may have contributed to the non-finding of the specimens.
15. The videoendoscope lens was covered with dirt when it entered the
anthill.
In order to fix this a PVC tube was settled around the videoendoscope`s
camera, which helped remove the dirt that covered the camera when it
was inserted. This solution improved the situation but it was not
completely solved.
16. Other problem was that the diameter of the
videoendoscope exceeded by a few millimeters the
diameter of the channel leading to the inside of the
anthill.
Therefore, the entering the videoendoscope inside
the anthill was detected by ants as if it was a threat
and made them mobilized in defense of their nest.
The breaks caused by the entering of the
videoendoscope in the anthill generated fragmenting
inside the mound.
This was contradictory, because the use of the
videoendoscope was thought for preserving each
anthill intact externally and internally during the
inspection.
If not, it was easier to inspect them only with a shovel
as it has been done before.
17. Another disadvantage was soil`s consistency. The study site was a flooded
zone, where regions were very dry or very wet. This model of videoendoscope
couldnot be submerged under water, making it difficult to use it when the ground
was wet. As its cable was slight flexible it was hard to enter it when the ground
was dry and hard. To solve this problem the PVC tube that was used to remove dirt
was used here too, to make it more rigid at the front and able to drill the
anthill, without breaking the camera. This solution was not helpful always this
problem happened.
18. Something to remark is that while the endoscope is flexible, it was very
difficult to follow the tunnels built inside the anthill within the inability to
move the end of the videoendoscope where the camera is, manipulating
the cable from a distance enough this part.
Probably, this could be solved with an articulated videoendoscope,
operated by remote control, for which the other problems should be solved
in order to design a specialized videoendoscope for such studies.
19. Studies will continue in 2013. Also new studies will be done in the
spring-summer period in order to determine whether anthills are
used as oviposition sites.
There are precedents for this type of studies conducted between
1987 and 1988, by staff of the Museum of La Plata and the
University CAECE in this study area, where the eggs found at that
time, belonged to two species of snakes: Philodryas patagoniensis
and Philodryas aestivus.
20. Acknowledgements
To my university FCNYM-UNLP because they granted me with a scholarship
for one year and I was able to do my first research project.
To the students that helped in field work: Nicolas Kass and Nadia
Hadir.
Special thanks to SIGMA XI "The Research Society" who granted me in
aid of research and made possibly to buy the videoendoscope.
