March 2010


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The frogs of Ben Lomond and Ben Ime have left their winter hide outs and are happily spawning in the (relative) warmth of the past week. Particularly at at the base of Ben Ime, near Arrochar, the frogs are out in force and spawn and adults can be seen in every pathside ditch and pool. The spawning continues all the way up to about 300m. As you can see below, this week I have observed many amplexing pairs that I have been weighing and measuring, along with the spawn being produced. Now if I could just get them to call so I could record them…

Another day in the field, sadly a rather drizzly one today, but still no spawning. I went to 3 different sites today, all at low altitude, and the temperature range was interestingly broad. It has highlighted to me the impact of aspect, shelter and location on local climatic conditions. The temperature at a low level pool at the base of Ben Heasgarnich was 4.8oC, but at Ben Dubhchraig was 1.3oC and still had a layer of ice. I did find one frog today, but sadly it was winterkill. I wonder whether the harsh winter means I’ll be seeing a lot more of these as ponds melt?

Yesterday I started my first day of fieldwork, beginning at the beautiful Ben Lomond. The frogs aren’t yet spawning (the water temperature ranged from 4.8oC at the base of the mountain to still frozen at 730m) but lack of ice lower down meant it was time to set up the temperature loggers. My supervisor, Barbara Mable and I set out dataloggers to measure air and water temperature at low, mid and high elevation pools (although water temperature can’t be measured at high altitude yet. The ice is still very thick and our best efforts couldnt break it). You can see in the photos the stakes that the dataloggers are attached to and the pools we will monitor.

Thanks to Alasdair Eckersall, the Property Manager and Ranger for Ben Lomond, we have a good idea of where frogs usually spawn on the mountain and have chosen sites to monitor accordingly. We also measured the conductivity and pH of the water bodies. Although I’ll be characterising the pool parameters fully later in the season, it is interesting to note that it was pH that varied the most between sites, with conductivity staying the same and temperature varying very little between the low (80m) and mid (427m) sites. There was still a fair amount of snow lying on the mountain and it will be a while before the high altitude frogs start breeding, but with the low level water being close to 50C I suspect the lower elevation frogs will start breeding in the next week. So start keeping your eyes open…

As winter draws on I begin to wonder whether the frogs will ever leave their overwintering locations and begin breeding. The literature suggests that common frogs need to experience a day at 5oC before their active season begins and they immediately head off to their breeding pools. As can be seen in these photos taken in the cairngorms a week or so ago, it certainly isn’t springtime in the mountains yet! It’s hard to believe that the frogs that live here must be somewhere below all this snow, buried in the ground or at the bottom of frozen pools. Common frogs are thought to withstand repeat freezing but not prolonged freezing, so we will have to wait and see how they have survived during this especially harsh winter. Spawning is already 3 weeks late for the low elevation frogs compared last year. This contrasts with the trend over the last decade of progressively earlier breeding. So I’m crossing my fingers for some warmer weather and looking forward to beginning my fieldwork.