Worcestershire Record No. 16 April 2004 pp. 21-22

Rosemary Winnall

Annual frogspawn counts have been made in the Wyre Forest for the last 17 years and we now have some valuable long term data based on work that was started by Mike Taylor in 1988 (see article in Wyre Forest Study Group Review 2003 by Rosemary Winnall, Sylvia Sheldon and Phil Rudlin). Although frogs and their basic life history are known by most schoolchildren, I found it impossible to locate much detailed information. So in the spring of 2004 I spent some nights and a day looking at a small group of breeding frogs in my garden pool. Luckily the spawning area is just below a small wall, which gave me the ideal view down into the clear water of the pool. My digital camera (for stills and movies) proved an invaluable tool for recording individuals and their behaviour. Many interesting observations were made giving me information that I had been unable to obtain from books or from websites.

I soon realised that the males and females could be distinguished easily both on appearance and behaviour. The males are active and conspicuous and lie with their legs spread in the water. They have white throats, thick front legs, and it is possible sometimes to see the swollen dark nuptial protuberances on the ‘thumbs’ of their forelegs. The females by comparison are retiring, have a hunched squat appearance and can be easily overlooked. They are often larger than the males, have swollen bodies of course prior to spawning, and their backs, thighs and sides are covered in pearly granulations from which the males identify them by touch. Their forelegs are thinner than the males, and their throats were darker, and never white in the ones that I observed.

I discovered that each frog has unique body markings and that one can soon learn to identify individuals. I built up a digital photo reference collection so that I could refer to the pictures easily and retain the information for coming years. I took shots with flash at night through the water by shining a torch onto the frog to focus the camera and got acceptable results for identification purposes. I photographed the backs of the males and the front of the faces of the females so that I could identify the individuals whilst they were in amplexus.

The breeding season was interrupted in 2004 by unseasonally cold weather, which meant that the pool was frozen when the spawn is normally laid at the end of February, and spawning did not take place until 16th March.

Male frogs were observed first at the bottom of the pool in early February and only came to the surface as the weather warmed. Each frog seemed to have its own area of pool, so thatI could predict their position. The females were visible later at the opposite side of the pool to the males. They tended to be amongst the weeds, with just their nose poking out of the water. They too were seen in the same places night after night. One pair was spotted in amplexus and these remained together right through the cold spell until their spawn was laid five weeks later. Another female was seen in amplexus with one male before the snow and ice, and ten days later emerged with a different male when spawning began! When the pair joins in amplexus, they seem to move around the pool and can be found anywhere from night to night, and within the same night.

Some of the females had a coating of mucous that was gradually shed as activity increased. I never saw this on a male.

After the 13 day cold spell, I resumed observations on 3rd March when the ice on the pond thawed. I was concerned to find that many of the males that I had identified in the middle of February were not visible. By the 15th March they had still not been seen, even though I was watching every night. However, once spawning commenced, they all arrived with a female in amplexus. So presumable they must have been out of sight amongst the weed.

Spawning commenced on March 16th when night temperatures were 11ºC. There was one tight clump of spawn at dawn on 16th March and this seemed to provoke great excitement and start the males croaking. The activity lasted all day, and I was able to observe frog behaviour in bright sunshine which made a change from lurking around in the dark with a torch!

The croaking occurred in bursts of activity, with periods of quiet in between. If there was any movement at the edge of the pool, all the males would rush across to investigate. This resulted in males clasping males until they presumable felt no body granulations and released their hold. There was one old male (Old Red we called him) that seemed to lurk around the bottom of the pool, less active than the rest. He was often seen clasping rounded pebbles with a dreamy look in his eye of perhaps past conquests – but more of him later!

Only once did I observe a female arrive at the spawning site alone. This was immediately after there were some odd sounds from between the stones at the base of the wall. I can only describe it as a gentle quacking – very unlike the usual croaking sounds. The female arrived quietly and was only recognised when one of the males touched her, seemingly by accident. He immediately grasped her and they swam around into the spawn. Old Red followed them closely. Within minutes she was laying her spawn, tight black eggs tinged with white. (They blackened completely within the hour). Old Red had his nose into the emerging spawn, and immediately it was laid he forcibly pushed the pair out of the way with his nose and proceeded to mount the spawn and from the look of his body movements, release his own sperm over the new eggs. This was completely unexpected behaviour. I watched two pairs spawning and Old Red repeated this behaviour on the second occasion too. He was never seen in amplexus.

The second time I witnessed the actual spawning was between Grump and his female. (I’ve been watching Grump for 2 years, and have photographed him in the pond in June 2003 and also when he spent a night sitting opportunistically under my MV moth trap all night in August last year). He arrived with his female and he was the only male I saw croaking whilst in amplexus. Just prior to spawning he also moved his head up and down on the back of the female in a sort of gulping movement. After spawning the now very thin female was immediately released and she swam away quickly and went out of sight under a stone. (I never relocated a spent female). Then Grump, with his back to the spawn, started vibrating his feet near the spawn. I wonder whether this was to circulate the sperm? Little did he know that it was probably the sperm of Old Red that he was moving!

In total there were only nine clumps of spawn laid, 17 frogs identified and probably two females unidentified. I look forward to next year to see how many of our fascinating frogs return!