Amphibian egg mass surveys across seven Metro natural areas wrapped up in April, revealing positive trends for these species. From January to April, Metro staff and 16 volunteers counted more than 500 egg masses.
The annual surveys involve crews scanning ponds as they wade through the water in straight lines, searching for egg masses from four amphibian species: northern red-legged frogs, northwestern salamanders, Pacific chorus frogs, and long-toed salamanders.
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Northern red-legged frog egg mass
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Northwestern salamander egg mass
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This effort is all about keeping track of how healthy the sites are. While the number of egg masses can fluctuate depending on the weather and other environmental factors, by counting them consistently at specific natural areas over several years, Metro can see if restoration efforts are working.
“It is important to note that what we observe is not always going to be exactly representative of breeding activity,” Metro wildlife biologist Katy Weil explained. “But we can say for sure that if we saw an egg mass, that meant one healthy pair of frogs or salamanders were there to make it happen.”
Why amphibians are important
Amphibians often spend much of the year in damp forests, making their way to wetlands during the breeding season. Because of this, healthy amphibian populations can be an indicator of larger-scale ecological health.
Beyond that, they play a crucial role in the larger ecosystem. “Amphibians are not very well understood – they may seem ‘squirmy’ and odd-looking – but they serve such a vital role within both forested and wetland habitats,” said Weil, who leads the egg-mass monitoring project. “Amphibians help keep insect populations in check, aerate the dirt in the forest, and feed many a hungry heron and other predator.”
Reflecting on the results
Fortunately, Metro’s data collection shows good news: The surveyed natural areas have been shown to better support expanded breeding habitat, holding enough water for tadpoles to mature by June. This is the result of restoration work funded by Metro’s voter-approved Parks and Nature bond and levy measures.
For example, at one natural area near the North Tualatin Mountains, crews replaced invasive reed canary grass with native plants, resulting in a surge in breeding activity. They also planted willows several years ago, and now those plants provide shade to keep the water cool. Areas of upland forest near these wetlands serve as overwintering habitat for the adult amphibians.
“We can adapt our restoration and land management to support amphibians by maintaining the trees and enhancing the seasonal ponds with native shrubs, which support egg-laying for amphibians,” Weil said.
It’s not always easy to make everyone happy. At another site, restoring fish passage habitat took priority, which meant reducing some of the still water in which amphibians like to lay their eggs. While it wasn’t ideal for amphibians, that stream now supports healthy fish populations.
“Every site is unique,” Weil continued. “We take a holistic approach, applying the best science to meet each habitat’s specific needs.”