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amphibians, frogs, salamanders, caecilians, newts, mudpuppies, waterdogs, axolotls, sirens, amphiuma, biology, physiology, genetics, distribution maps, zoology, conservation, preservation, biodiversity
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Article 0007 Species Mixing: New World Syndrome
Introduction
The title of this article is a reminder of the dangers of introducing
foreign pathogens to new species or races. When European's began to colonize the America's in the 15th century, they brought
with them foreign pathogens, including small pox and the common cold, that Native Americans
had never been exposed to. Because of their isolation from these
pathogens, Native Americans did not have natural
resistances to these illness, and the majority of those infected died
horrible deaths. Smallpox and other
illnesses were the primary cause of Native American declines from the 15th-18th
century, and wiped out thousands of people. History has taught us a painful
and devastating lesson about foreign disease, the immune system, and the
devastating result of introducing foreign pathogens to unexposed victims. The
end result is the same when different amphibian species are housed in the
same captive environment. In fact, it's countless times worse because
captive environments are so minute compared to wild habitats, which allows
for a microbes to multiply at a phenomenal rate.
Of course there are many species that live in close proximity with other
amphibian species, and in many cases housing such species together is okay.
What really causes health problems is when species from different habitats
and environments, and from different geological locations are housed
together.
In addition to the risks of foreign pathogen exposure, animals of
incompatible size, disposition, and behavior are housed together, which is
simply a recipe for disaster.
Below is a list of common mixed-species scenarios, and
the reasons they are harmful and potentially fatal to amphibians:
Housing geologically isolated species together
The most common reason amphibians become ill in a mixed species environment is due to the introduction of foreign pathogens
from species from different areas of the world. In the wild, species are exposed to numerous
local pathogens, such as bacteria or virus strains, fungi, and other harmful
agents, and through evolution have developed
natural resistances/immunities
to them. However, because these pathogens vary greatly from one location to
another, the natural resistances developed by any particular species also
varies greatly and is dependent on that species immediate wild habitat.
Again, the case of European invasion and the effect of European pathogens on
Native Americans can be referenced. For
example, a newt from the United States, such as N. viridescens, will
have developed resistances to different pathogens than a species
from another environment, such as the Chinese Fire
Belly newt, C. orientalis. A species will still carry the pathogens
for which it has natural resistances to, so when one species is introduced to
a foreign species, those pathogens and other harmful agents are inevitably
being introduced to each species, which typically ends up
in the illness or death of one or both due to their lack of natural
resistances (i.e. New World Syndrome).
Pet stores often house several salamander and newt, and sometimes frog, species in one tank, which gives pet buyers the
idea that amphibians are community
animals and coexist in a closed environment with other species. Unfortunately, these
animals are often ill when purchased and die shortly after due to their mixed-species environment. It
is true that some have mixed certain species with no ill effects for several
years, but it is very risky doing so, and not the behavior of responsible
keepers.
It is also a common misconception that captive bred species are
exceptions to the rule, and can therefore be housed with other amphibians
species. The fact is that animals are not sterile creatures, and even
captive bred species carry harmful pathogens. Granted, captive bred species
are less likely to carry the same diseases and parasites as wild caught,
however it's still risky to house even captive bred foreign species
together.
Listed below are some all-too-common mixed species scenarios, with additional information
as to why these setups are particularly disastrous.
Housing Newts with Fire-Belly Toads
Many pet stores and pet buyers house their newts with
fire belly toads (Bombina spp.). Aside from the issue of
foreign pathogen introduction, fire belly toads are aggressive eaters, and often
injure small newts in the process of lunging at food. In fact, they
are aggressive and territorial all the way around, and will most
likely end up injuring small newts even if separated during feeding
time. I have heard
countless accounts of newts with wounds or missing limbs because of
aggressive fire belly toads, the consumption of the newts by the
toads, as well as cases of starvation because the
toads are such aggressive feeders that more passive newts
never get any food.
Housing Fire Belly Newts (Cynops) with
Eastern Newts (Notophthalmus)
Although these newts are roughly the same size, require nearly the same
captive habitats, and have the same peaceful disposition, they are
still from opposite sides of the globe and carry different pathogens
for which the other has no resistances too.
Housing Newts with Tropical Fish
Often, newts are purchased and thrown into tropical fish tanks,
where they soon die and/or kill other members of the tank. Tropical fish require warm water temperatures
(72°F-86°F), and caudates
require cooler water temperatures (62°F - 68°F).
Their habitats simply are not compatible with each other. Also, many
fish have
the tendency to nip at passive creatures, such as newts, and because
newts are poisonous, this can kill the fish. Finally, all newts
require a land area of some sort (even if it is only used for two
minutes out of the year).
Housing Newts and Salamanders with Frogs
Salamanders and most frogs are solitary
creatures, and become stressed when forced to live closely with
other species. When salamanders are stressed they often reject food,
which leads to malnourishment and starvation. The same can be said
for frogs. Some species
are more aggressive than others, and will harm more passive species.
Many frogs
require high temperatures (75°F-85°F), and caudates require cooler
temperatures (62°F - 68°F). And of course, foreign species carry
different pathogens for which the other has no resistances too.
Housing Frogs, Salamanders, and Newts with Turtles
Turtles create an enormous
amount of waste products for their size. This alone can lead to the
illness of any amphibian. Turtles are also very aggressive feeders and
could seriously injure a caudate while feeding, or simply consume
the newt. Most turtles will
far surpass most amphibian species in size, which will lead to
starvation of the amphibian, and injuries. Also, the aggressive
behavior of turtles may stress the amphibians, causing them to
reject food.
Other consideration when choosing tank mates
Aside from species mixing, there are other considerations when housing
sympatric (different species from the same range) or conspecific (same
species) species together. The size and
behavior/disposition of each member must be considered. Large individuals
will dominate small ones, and sometimes pick on them and prevent them
from getting any food. All members housed together should be of roughly the
same size to ensure one is not bullying the others. Adults, juveniles, and
larvae should be housed separately to avoid cannibalism. Aggressive and
territorial species should be given ample territory, or should be
separated. Caudates of the genera Pachytriton and Paramesotriton,
for example, grow rather large, are very aggressive and territorial, and can
easily kill smaller members. Pachytritons in particular are territorial, and
have been known to fight to the death if not given enough territory.
So, What can be Housed with Newts, Salamanders, and
Frogs?
Obviously, amphibians are not isolated from other animals in the wild, and certain amphibian species will tolerate a few other
organisms in their captive environment. Conspecific and even sympatric species
can generally be housed together in spacious tanks. Some
species of aquatic and semi-aquatic amphibians will tolerate small guppies, white cloud minnows, ghost
shrimp, or apple snails in their water area. Keep in mind that fish can also introduce
foreign pathogens that amphibians may be susceptible to. Also keep
in mind that the tolerance of fish varies from species to species. Eastern Newts, N. viridescens,
for example, are mostly
aquatic in adulthood, but prefer fishless waters and will often
reject waters will fish in them, even guppies. More robust species,
such as those of the genus Paramesotriton, on the other hand
don't mind a few guppies in their homes, and will even eat them. Terrestrials can reside
with earthworms, which are actually beneficial for soil terrariums,
and which may also provide food for larger amphibians.
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