Beaver
and Amphibians
Note:
This online review is updated and revised continuously, as soon as results
of new scientific research become available. It therefore presents
state-of-the-art information on the topic it covers.
When beaver (Castor canadensis and Castor fiber) build dams and
create impoundments (ponds), certain groups of amphibians are benefited
while others are harmed. For
example, in
the Piedmont of South Carolina, frogs were twice as abundant along streams
with beaver impoundments than along streams without beaver
impoundments (Metts et al. 2001).
In contrast, salamanders were ten
times more more abundant along streams without beaver impoundments
than along streams with beaver impoundments (Metts et al. 2001). Although,
generally speaking, frogs are benefited by beavers and salamanders are
harmed, there are some exceptions. Let us look now at which
specific frogs and salamanders are benefited and harmed by beaver
engineering.
Amphibian
Species benefited by
Beaver Engineering
In
the Piedmont of South Carolina, the following species of amphibians were more abundant along
streams with beaver impoundments than along streams without beaver
impoundments (Metts et al. 2001):
Northern Cricket Frog
(Acris crepitans)
Green
Frog (Rana clamitans)
Pickeral Frog (Rana palustris)
Southern Leopard Frog (Rana spenocephala)
American Toad (Bufo americanus)
Some
of these species, such as the American Toad and Pickeral Frog, use a
variety of aquatic habitats, but are "most abundant along the grassy,
open margins of ponds, marshes and ditches" (Metts et al. 2001).
Hence it should be no surprise that they are more abundant where beaver
have slowed the flow of streams by building dams and creating
impoundments.
An
additional species, the
Green Treefrog (Hyla cinerea), has recently colonized the Piedmont of
South Carolina and all of its known populations there are also found at beaver
impoundments (Synder and Platt 1997; Platt et al. 1999; Russell et al.
1999). This frog prefers the aquatic vegetation around pond
edges that is characteristic of old beaver ponds (Russell et al. 1999).
In
the littoral zone of headwater lakes in northwestern Ontario, the Red-spotted Newt (Notophthalmus viridescens)
was more abundant near beaver lodges than in adjacent sand-rock habitats
(France 1997).
Almost 100% of the large diving beetles, hemipterans, and newts in these
lakes were associated with beaver lodges (France 1997). This
researcher concluded that in boreal headwater lakes, where large aquatic
plants (vascular macrophytes) are rare, beaver lodges may be important in
structuring littoral communities.
Amphibians Harmed by Beaver
Engineering
The following species of
amphibians in the Piedmont of South Carolina were more
abundant along streams without beaver impoundments than along
streams with beaver impoundments (Metts et al.
2001):
Northern Dusky Salamander (Desmognathus fuscus)
Mountain Dusky Salamander (Desmognathus monticola)
Seal Salamander (Desmognathus fuscus)
Blackbelly Salamander (Desmognathus quadramaculatus)
Southern Two-lined Salamander (Eurycea cirrigera)
Northern Spring Salamander (Gyrinophilus porphyriticus)
Jordan's Salamander (Plethodon jordani)
Red Salamander (Pseudotriton ruber)
Some
of these salamanders (e.g. Desmognathus spp.) are typically found
in springs, brooks, and small streams, and can not live in slow-moving
streams, ponds or beaver impoundments where predatory fish occur (Metts et al.
2001). Others, like the Red Salamander, are woodland species that
might need the "greater cover and depth of leaf litter"
associated with forests not cut by beavers (Metts et al. 2001).
Habitat Shifts by
Amphibians
The Wood Frog (Rana sylvatica)
and Spotted Salamander (Ambystoma maculatum) typically breed in
seasonal pools of water, but may use permanent ponds that lack fish.
In contrast, they usually avoid permanent ponds with fish, because fish
eat the offspring of amphibians.
In
4 national parks of southern USA (North Carolina, Tennessee and Kentucky),
the effects of beaver engineering on these 2 amphibians depended on
whether or not the engineering altered the distribution of fish (Petranka
et al. 2004).
For example,
if a newly-created beaver dam did not contain fish, the frog and
salamander often moved into it and bred there until it was invaded by
fish, after which the amphibians declined or disappeared.
If, on the
other hand, a newly-constructed beaver dam created a pond with fish, and
if the rising waters of this pond created a water connection to a nearby
temporary pool of water used by the salamander and frog, the fish invaded
the temporary pool, causing the amphibians there to decline or disappear.
References
France
RL (1997) The importance of beaver lodges in structuring
littoral communities in boreal headwater lakes. Canadian Journal
of Zoology 75: 1009-1013
Metts
BS, Lanham JD, Russell KR (2001) Evaluation of herpetofaunal
communities on upland streams and beaver-impounded streams in the upper
piedmont of South Carolina. American Midland Naturalist 145:
54-65
Petranka
JW, Smith CK, Scott F (2004) Identifying the minimal
demographic unit for monitoring pond-breeding amphibians.
Ecological Applications 14: 1065-1078
Platt
SG, Russell KR, Snyder WE, Fontenot LW, Miller S (1999) Distribution and
conservation status of selected amphibians and reptiles in the
Piedmont of South Carolina. Journal of the Elisha Mitchell Scientific
Society 115: 8-19
Russell
KR, Moorman CE, Edwards JK, Metts BS, Guynn DC (1999)
Amphibian and Reptile Communities associated with beaver (Castor
canadensis) ponds and unimpounded streams in the piedmont of South
Carolina. Journal of Freshwater Ecology 14: 149-158
Skelly
DK, Freidenburg LK (2000) Effects of beaver on the thermal
biology of an amphibian. Ecology Letters 3: 483-486
Snyder
WE, Platt SG (1997) Anuran records from the Piedmont of South
Carolina, USA. Herpetological Review 28: 53
Information
about this Review
The
author is: Dr. Paul D. Haemig (PhD in Animal Ecology)
The photograph at the top of the page was
taken by Peter Hamza (Hungary). It shows
a frog, one of the amphibian taxa benefited by beaver engineering.
The
proper citation is:
Haemig
PD 2012
Beaver and Amphibians. ECOLOGY.INFO #14.
If
you are aware of any important scientific publications that were omitted
from this review, or have other suggestions for improving it, please
contact the author at his e-mail address:
director {at} ecology.info
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