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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