Amphibian Life Histories
Amphibians include frogs, toads, salamanders, and legless caecilians,
and are characterized by shell-less eggs, highly permeable skin and a
complex, bi-phasic life cycle. While a few amphibians are fully
terrestrial, amphibians of the Palouse spend their adult life on land
and return to ponds or streams to breed. Their eggs are laid in water
and hatch into free-swimming larvae equipped with gills for
respiration. Developing in water enables amphibians to exploit a rich
food base in a relatively constant thermal environment. However, their
aquatic environment is not without risks: predators abound, including
dragonfly larvae and amphibian adults and larvae; and their pond may
dry up altogether, sometimes before metamorphosis is complete.
Successful larvae undergo metamorphosis and move back onto land as
adults. Metamorphosis requires dramatic changes in morphology and
physiology when larvae change to lung-breathing animals. Once out of
water, amphibians face new problems, including a new set of predators,
fluctuating temperatures and humidity, and changing habitats (Mitchell
2000).
Like canaries in the coalmine, amphibians are believed to be important
indicators of environmental health (Olson et al. 1997). Their permeable
skin, lacking a protective covering of fur or feathers, makes them
vulnerable to chemical pollutants and radiation. Furthermore, their
bi-pahsic life cycle subjects them to environmental hazards both on
land and in water (Beebee 1996).
Handle with care!
Let’s not be part of the problem. Several of our Palouse amphibians are
listed as sensitive species by federal and state agencies and private
conservation organizations. It is best not to handle them at all, and
if it is necessary to handle them for identification purposes, to
follow the proper handling protocol. Be certain to also consult page
... of this manual for procedures to avoid the spread of amphibian
diseases.
Detailed information on the proper handling of amphibians is presented
on the website of the at American Society of Ichthyologists and
Herpetologists. A brief summary of suggested handling protocol
follows.
- Make sure your hands are free of lotions. Insect repellent,
suntan lotion, or toxins from a previous amphibian can be harmful to
amphibians.
- Keep the animals cool. If you must handle an amphibian for a
long time, moisten your hands periodically, let the animal rest in a
plastic bag or covered container, and replace the cold water in the
container.
- Amphibians dry rapidly during handling. Wet your hands with
pond water before handling the animal, and handle it as briefly as
possible.
- A frog can be held securely if you first hold it in your
fist, let it wriggle forward, then gently hold the legs together while
you support the body. Don’t squeeze, please!
- When handling salamanders, avoid contact with the tail,
which can break off easily. Tail loss may have a significant effect on
survivorship, reproduction and dominance interactions. Salamanders
become more active as they warm up in your hand. To keep it moving
slowly, put the salamander on your work glove, which is usually cold
and wet, or on a leaf or piece of bark.
- Newts have the most toxic poison of any amphibians in our
region – a potent skin toxin called "tetrodotoxin" that is
chemically identical to some puffer fishes. People have died from
accidentally boiling a newt in their camp coffee pot. Be sure to wash
your hands thoroughly after handling a newt – before eating your lunch
or rubbing your eyes.
- To examine hatchlings, larval salamanders and tadpoles,
place them in clear plastic containers. Do not keep tadpoles out of
water for more than a minute, and do not squeeze tadpoles. They are
turgid with water and may burst open. Larvae and tadpoles are best
observed against a white background.
- Return the animal exactly where you found it. Some
amphibians have home ranges of only a few meters square, and may expend
valuable energy trying to make it back home once displaced.
Avoiding the Spread of Amphibian Disease
If you travel between your pond and any other pond site, you will need
to take precautions not to transmit amphibian diseases via your boots
or equipment. Complete information on appropriate protocol for avoiding
transmission of disease between sites is detailed in the Declining
Amphibian Populations Task Force (DAPTF) Fieldwork Code of Practice at
www.npwrc.usgs.gov/narcam/techinfo/daptf.htm
You are encouraged to read the above document. At the very least, be
sure to follow these rules:
- Thoroughly clean your boots, gloves and any trapping equipment with
a scrub brush, toothbrush and toothpick if necessary, to remove all mud,
snails, algae and other debris.
- Scrub boots and equipment with a 70% ethanol solution, and
rinse with sterilized (boiled or treated) water before leaving the
site. Avoid cleaning equipment in the immediate vicinity of the
wetland.
- Participants in MAP are advised to discontinue work in areas of
known or suspected disease problems. Proper protocol for working at
such sites requires wearing disposable gloves and changing them between
handling each animal. It is suggested to dedicate sets of nets, boots,
traps and other equipment to each site being visited.
- If amphibians are collected, ensure the separation of animals from
different sites, and take great care to avoid indirect contact between
them. If amphibians are raised in a classroom or home, it is best to
not return those animals to the wild. If it is necessary to release
them, return them to the pond from which they were collected.
- Used cleaning solutions should be disposed of safely. Used
disposable gloves should be retained for safe disposal in sealed
bags.
These measures may sound extreme, but it is important to note that
observations of diseased and parasite-infected amphibians are being
frequently reported from sites around the world. It is important that
those of us studying amphibians do not contribute to their demise.
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