Monday 28 February 2022

The Frogs of Lye Valley 26th February 2022

On Friday the 25th of February I rose early to go to the Lye Valley Nature Reserve which forms part of a shallow and narrow valley, sandwiched between housing and a hospital, at Headington in the City of Oxford. I had been told by a friend that the frogs had returned a few days ago, as they do every year, to mate and spawn in a series of four small, shallow ponds running alongside a boardwalk that bisects the valley 

The reserve is in existence mainly to preserve twenty rare species of plant that grow there, chief of which is the Grass of Parnassus but the rare fenland in which they grow, fed by the Lye Brook and lime rich springs, is also favoured by breeding Common Frogs for a brief few days in early Spring and that is the main attraction for me.

The Lye Valley NR consists of exceedingly rare fenland, an eight thousand  year old, internationally rare habitat of which the Lye Valley represents 1.5 hectares of only 19 hectares of this habitat remaining in England. It is a designated SSSI (Site of Special Scientific Interest) due to the rare and endangered plants that grow there and is a joint project between Oxford City Council and BBOWT (Berks, Bucks and Oxon Wildlife Trust).Conservation work is carried out by The Friends of Lye Valley.

Part of Lye Valley Nature Reserve and one of the small ponds that harboured the breeding frogs

The night, prior to dawn on Friday, had been very cold with a severe frost and although it was going to be sunny all day it would take some time for the sun to rise high enough to reach the floor of the valley. Due to social commitments I had only a couple of hours to visit in the early morning and on arriving and walking down into the valley and along to the boardwalk, I knew I was probably going to experience disappointment. 

The small ponds were covered by a wafer thin covering of ice with just a small area of unfrozen water in one of the ponds. Needless to say there was no sign of any frogs. I sensed that the ponds were  too cold for any frog activity and they were all lying at the bottom of the ponds. There was, however already plentiful evidence of breeding, with mounds of jelly like spawn, encrusted with frost, in one of the frozen ponds.

A series of ripples in the patch of unfrozen water alerted me to the presence of frogs and I could see three or four swimming under the water but they were sluggish and certainly not inclined to come to the surface. After an hour of waiting I retreated, somewhat chastened and having learnt the hard way that frogs are not active in such low temperatures.

I resolved to return the next day, Saturday, at a later hour when the sun would be higher and presumably the water temperature warmer. I arrived at the ponds just before 11am but again found little sign of any frogs until eventually some poked their bug eyes above the water in one of the ponds. Fifteen minutes passed, more appeared and frogs began croaking as the preponderance of males competed to attract the fewer females. Gradually numbers built up until there were around twenty frogs visible and I focused my attention solely on their activities.

Half an hour passed happily, photographing the frogs but then, glancing to my right, towards the next pond, I was amazed to see at least fifty frogs swimming and poking their heads above the surface of that pond too.The sun was now shining fully on the ponds and presumably the frogs were responding to the rise in temperature and setting about the process of mating and spawning with alacrity.They were totally absorbed in reproducing and showed none of their customary shyness and secrecy, apparently so consumed with the urge to mate and spawn they were heedless of the many dangers they routinely face from numerous predators. They are obviously very vulnerable in this situation and the sooner the process is completed the better for them so they can return to their secret hiding places, away from the pond and where they will be more secure.

By noon the numbers of frogs had built up to over a hundred, the pale throats of the male frogs, distinctive in the sun as their heads protruded above the water, their throats swelling as they produced a  rhythmic accompaniment of incessant, quiet croaking, a not unpleasant purring sound rather like hearing a distant moped.

There was a noticeable diversity in the individual frogs colouring, some reddish brown while others were green, yellowish, even grey, their skins patterned with spots and markings varying from black to lemon yellow. No one frog looked quite the same as another. The females were obvious, appearing much larger than the males due to their bodies being swollen with spawn and also more colourful, with reddish brown throats speckled with yellow. 

A female attended by two male frogs

There were frequent brief tussles as the more numerous single males attempted to usurp a male already clinging to a female's back,  a process called amplexus, where the male clings to the female with his front legs in a vice like grip, ready to fertilise the eggs the minute the female expels them from her body. Once a male is attached to a female's body, nothing can remove him although other male frogs try as hard as they can to do so.

The pond was by now a scene of constant activity as the frogs blundered around in the water or lay in the masses of spawn as if in a bubble bath,.There is but one thing that drives them at this time and that is the urge to procreate by actively seeking a female or just hanging in the water with head held clear and croaking endlessly which is the way they attract females, with presumably the female selecting a partner based on the quality of his croak. 

It is for only a few precious days that this spectacle endures, and spectacle it is, attracting numbers of people to the boardwalk, both adults and children who, like myself, come to see and marvel at this natural phenomenon. Soon the ponds will fall silent and all that will remain is the 'frog spawn' that will hatch in two or three weeks and fill the ponds with black tadpoles. 

I will have to wait another year and for another early spring day to renew my acquaintance with the frogs of  Lye Valley but today's experience of watching nature's relentless renewal of life during these dark times was, for me, life affirming and I departed feeling all the better for it. 

Here are some more images of the frogs that I saw on the day.

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