First One to Blink?

 

Spotted the first frog of 2025 in our small garden pond on February 22nd. This is exceedingly good news because it means at least one has survived the winter. For the past two years (2023 & 2024), we had no frogspawn in the pond but did, unfortunately, find deceased amphibians.

There could be any number of reasons why we did not get frogspawn in certain years - the most obvious being that we had no breeding frogs (perhaps they found better accommodation elsewhere!). Apart from disease (fungal, viral and bacterial) and predators (herons, rats, cats?), winterkill may be significant. Frogs may overwinter at the bottom of a pond, absorbing oxygen through their skin. Decomposing vegetative matter in the pond will consume some of the dissolved oxygen in the water - this becomes an issue if the pond freezes over, preventing fresh oxygen from the air replenishing the consumed oxygen, and producing anoxic conditions.

In the Figures below, daily minimum temperatures are shown for the past 6 winter seasons (December, January & February). The temperature scale (y-axis) runs from -10 ℃ to +15 ℃. Click on the images to enlarge.

Figure 1: Minimum Daily Temperatures (2019 - 2020 Winter)

Figure 2: Minimum Daily Temperatures (2020 - 2021 Winter)

Figure 3: Minimum Daily Temperatures (2021 - 2022 Winter)

Figure 4: Minimum Daily Temperatures (2022 - 2023 Winter)

Figure 5: Minimum Daily Temperatures (2023 - 2024 Winter)

Figure 6: Minimum Daily Temperatures (2024 - 2025 Winter)

Only two winters (2022-3 and 2023-4) had temperatures below -5 ℃ which coincided with no-shows for frogspawn.

In future, we need to ensure the pond does not freeze over for extended periods. For example, by adding a ball that floats and then removing it should the pond freeze over to leave a hole for oxygen ingress.