Can toad patrols make a difference?
(Feedback from Steve Rogers who acts as coordinator for the Osmotherley Toad Rescue on behalf of the charity Froglife’s “Toads on Roads” project.)
The short answer to a question about the impact of toad patrols on their population is that conclusive evidence cannot be drawn, one way or the other, from the available data. There are too many other variables (see below) to permit this. We did have a couple of significant increases in toad numbers for the pairs of years 2002-2003 (when we started patrols), 2004-2005 and 2009-2010 but whether these were due to our patrolling I cannot say. Figure 1 is a summary of the numbers for each year. The site is currently in Froglife's top ten breeding sites in the UK and may have been top five in the early 2000s.
I will state, at the outset, that it is difficult to see how toad patrols could conceivably damage toad breeding success. We believe that toads migrate quite large distances, maybe over several days, across the Moors from their summer residences/hibernation sites (indeed we patrol only the road side of the reservoir and it is quite possible that similar numbers come off the Moor or out of the woods on the non-road side). We are merely helping them to move the final, hazardous metres to enter (or exit) the water. Furthermore, we are helping to bring males and females into contact ready to breed by collecting them in numbers in a bucket.
One thing is clear is that frog numbers have declined very significantly, possibly due to disease - "red leg" (Bacillus hydrophilus fuscus) and Chytrid fungus (Batrachochytrium) - though we have not seen direct evidence of either, except possibly one or two specimens. However, disease is not entirely certain as the cause of the decline since frog movements often occur before we manage to get patrols organised (on horrible cold, wet nights in late February when even I find it difficult to be enthusiastic!)
Numbers of newts (which we believe to be Palmate) have fluctuated greatly and newts may also have been affected more recently by Chytrid (though no evidence seen by ourselves).
The trends in toad numbers are difficult to assess because of the multiple variables involved. If I had to guess, I would say that order of importance of such factors for any given year is as follows:
We have experienced a series of very cold, often dry spring conditions. Toads generally do not move if the temperature is below about 8 C (though if it has been warm during the day they may move briefly at dusk with the temperature as low as 4 or 5 C). During a "normal" spring this threshold is reached around mid-March. What has happened in several years is that migration has begun in a brief period during mid-March but then the weather has turned colder for several weeks and stopped any movement. This makes it very difficult to forecast when it will be worth patrolling and, indeed, to keep volunteers motivated. Extreme cold conditions prevailed in 2013 when temperatures did not become suitable for migration until mid-April. Figure 2 is a graph showing how toad numbers have accumulated over each year that we have patrolled. A further feature worth noting is that, when toad migration has been inhibited by low temperatures for several weeks, movements also occur during daylight hours when it has been warmer. Of course, with higher traffic volumes during the day the numbers of casualties are greatly increased (e.g. 2007, 2011 and 2012). Our best year was 2005 when we had a consistently mild spring and all movements took place over a couple of weeks.
2. Diligence of Patrols
During the first few years we had very adequate numbers of volunteers and patrols were admirably thorough (the learning curve for patrollers is steep but quite easy providing the weather plays ball). As years have gone by the numbers of volunteers decreased to a very few individuals until last year when I finally got around to instituting a publicity/recruitment drive. I am very grateful for the new volunteers last year who came exclusively through NYMNPA contact. These new volunteers were extremely diligent and we had our lowest mortality rate since the heydays of 2005 (see table). It remains to be seen if we have adequate numbers of volunteers for 2015.
3. Other one-off factors
There have been a number of events during individual years which I think have had significant impact on toad populations:
2001 - Foot and Mouth disease led to complete closure of the road during the migration period.
Obviously good for toads and may explain why the start of our formal patrols in 2002 found large numbers.
2004 - A large fire burnt the National Trust moorland (West side of the road) on 29th March. We found a number of incinerated toads and injured animals and this may explain the drop in numbers compared with the previous year, though the following year (2005) was our all-time peak (7,325 toads).
2009 - A major rescue operation occurred on 5 April which was mild and wet and was the most significant toad movement for that year (we can get up to 1000 toads recorded on such a night). This was the night that Claudia Lawrence had been reportedly seen on the local moorland following her disappearance from York. Many rescue vehicles arrived early in the toad patrol to park at Sheepwash and I had to abandon as it was not safe. The following morning I removed 349 toad corpses from the toad surface and the mortality rate for that year was much higher than usual. Unfortunately, poor Claudia Lawrence is still missing.
2011 - Yorkshire Water drained the breeding site (Cod Beck reservoir) in order to carry out maintenance work on the dam. Water levels were several metres lower than normal and I believe this greatly affected breeding success (toads breed in deep water). The surface of the reservoir was reduced to perhaps 1/3 or 1/4 of its norm. The following year was the absolute nadir in toad numbers being a factor of 2 lower than any other year. Numbers have not recovered to pre-2011 levels since. I dread the rumours that Yorkshire Water wish to dispose of the property, draining the reservoir in order to make this more attractive.
I have tried to be objective in my analysis since the data does not really permit me to carry out any proper statistical studies.
Regarding new volunteers, I prefer to have them come from within a reasonable travelling distance. The reason is that we cannot predict accurately, until maybe the day before or even on the day, whether it will be worth a volunteer turning out in the evening. I'd hate to drag someone from 50 miles away to find no toads appear. We do have regular volunteers from Darlington and Guisborough areas and I think that probably represents a reasonable limit. But, of course, it is up to the individual and it's usually a nice place to spend a couple of hours in the dusk.
If you would like to volunteer to help with the Osmotherley Toad Patrol then please come to a pre-season meeting at the Queen Catherine pub in Osmotherley at 7:30pm on Wednesday 18 February. More information will be given out, including a form that gives volunteers free insurance (thanks to Froglife) whilst carrying out patrols. If you are interested but can’t make the meeting please email Steve Rogers at firstname.lastname@example.org, preferably before the end of February.
Alternatively, you can show your interest by going to this website http://www.froglife.org/what-we-do/toads-on-roads/tormap/ and entering Osmotherley in the box marked “My Location”. This will take you to map of the local area around the toad patrol plus a link to offer to help. There is a lot more information about Froglife’s “Toads on Roads” project here - http://www.froglife.org/what-we-do/toads-on-roads/.
Updated information February 2016:
A cold snap in March 2015 saw a delay in significant amphibian movements until the beginning of April. We then had a busy two weeks rescuing 3576 toads, 84 frogs and 116 newts. All these numbers were higher than in 2014 and it was easily the best toad year since 2010. Volunteers are always welcome to join us.
Updated information January 2017:
March and April 2016 were dry and cool for most of the time which inhibited toad migration. Despite having experienced, dedicated patrols the numbers of toads were low at 1527, our worst year since 2012. Frogs and newts do not seem to be so sensitive to cold and their numbers were up at 115 and 121 respectively. It is particularly heartening to see increasing numbers of frogs following declines which were possibly due to disease such as ranavirus, and chytrid fungus.
New volunteers are always welcome to join us.