Amphibian Science

Both aquatic and terrestrial

Amphibians are important indicators.

Newts, salamanders, frogs, and toads.

There are 32 amphibian species in Oregon – all are native to the state but one: the American bullfrog. The American bullfrog can compete with – and even prey on – native many native turtles, frogs, fish, and snakes!

Many of our native amphibians are classified as sensitive – either vulnerable or critical – so possessing them is not legal. But there is often a lack of even basic data for many species! Our work has actually identified areas in need of restoration and protection.

What we’ve discovered together –

We’re documenting the unknown!

946

Egg Masses in 2023

13

sites surveyed

1

species of concern

Amphibians can live both on land and in water – a unique feat in the animal kingdom!

Amphibian Surveys

A variety of habitats is needed for the different species – there is no one-size-fits-all.

Life History

Although we usually associate amphibians with ponds, most amphibians spend at least part of their lives on land. In fact, many species winter on land, hiding under debris, like vegetation, leaf litter, and logs.

Amphibians can “breathe” through their skin (they also have lungs). To absorb oxygen through their skin though, their skin needs to be wet. So, they secrete mucous to keep their skin moist and use habitats where there is a lot of moisture.

Water is a general requirement for breeding and egg laying, although some salamander species are completely terrestrial – laying their eggs on land.

Species Diversity

Oregon’s amphibians are grouped into one of three categories based on their habitat requirements and life histories: amphibians inhabiting slow-moving waterbodies, amphibians inhabiting medium to fast-flowing streams, or terrestrial salamanders.

Salamanders are tailed amphibians with long bodies and short limbs. Some may be completely terrestrial, but they still prefer moist habitats. Oregon has 19 species of salamanders.

Frogs and toads tend to be short-bodied and squat. Frogs are more slender than toads and have smooth skin. Their eyes are higher on their heads than a toad’s eyes. Toads are wide-bodied and have dry, rough skin. Toad eyes are rounder and bulging.

Oregon has 12 native species of frogs and toads, many of whose population sizes are of concern. Worldwid, many frogs are endangered, a result of climate change, habitat loss, pollution and pesticides, infectious diseases, invasive species – and the pet trade.

Methodology​

The goals of our amphibian egg mass surveys are to determine whether urban stormwater ponds are working as habitat or not and what we might do to change them.

Surveys are conducted in February and March. Our local amphibians prefer to breed on the edges of vegetation patches, so while some vegetation is necessary for amphibians to attach their egg masses to, too much vegetation can crowd amphibians out of ponds.

Sites and methodology were developed with help from Katie Holzer, Watershed Scientist, City of Gresham.

Dragonfly larvae can be significant predators on amphibian tadpoles, so much so that they can influence the evolution of species color and shape!

2022 Results

Of the ponds surveyed this year, 85% had red-legged frogs! Red-legged frogs are a species of conservation concern in Oregon, and urban ponds are apparently important habitat for them.
 
Some of the older ponds, those that are filling up with sediment and vegetation, seemed to show declines in the number of egg masses. Many of the newly-constructed ponds had abundant egg masses, however, indicating that some stormwater ponds may require dredging and maintainenance. In natural habitats, flooding and beaver activity change the landscape constantly, creating new ponds with young vegetation.

Based on total numbers of egg masses, most species seem to be doing fine, but red-legged frog populations may be declining. Populations flucuate from year to year, and assessing a population trend requires at least 10 years of data. Also, that trend is being driven by just a few formerly productive ponds that may be filling in with sediment. Future efforts will focus on these ponds.

The median number of egg masses found each year at each site are fairly consisent, indicating that the populations are likely stable. Northwestern salamanders don’t do well in urban areas, and they were rarely found. As a result, the median mass size zero.

The maximum number of egg masses for each species at each site were:

Overall highest for all species combined –
Brookside (B) with at least 436 egg masses

Most northern red-legged frog egg masses –
Kelly Creek Detention East Cattail Pond (N) with at least 54

Most Pacific treefrog egg masses –
Sunset Village (S) with 310!

Most northwestern salamander egg masses –  
Woodlawn Cemetery Pond (F) with 2

Most long-toed salamander egg masses –
Jasmine Way (J) with 119

Runners up:

Red-legged frogs
Gabbert Butte (G), Jasmine Way (J), Brookside (B), Hogan Butte (H)
 
Treefrogs
Brookside (B), Border Way (A), Meadowlands (M), Hogan Butte (H)
 
Northwestern salamanders
Dowsett Ditch (F), MHCC East and Pothole Ponds (L), Brickworks South (P), Gabbert Butte (G)
 
Long-toed salamanders
Meadowlands (M), Panza (R), Brookside (B), Brickworks South (P)

Amphibians are “cold blooded.” That means the animal’s body temperature is essentially the same as its surroundings.

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