RAUK - Archived Forum - Posts by Gemma Fairchild:

All,

I have wondered to what extent our native reptiles and amphibians are suffering from inbreeding depression.

With continued habitat loss and increasingly isolated populations, what are peoples views on the relative merits of captive breeding of out-bred animals, for release, and the translocation of adults from thriving populations into inbred populations to help combat the effect?

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Hi Wecki,

Thank you so much for your early support of the RAUK forum and linking it up to the whose-tadpole site

Regards,

Gemma

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The only article I am aware of concerns a small population of Vipera berus, that appeared to benefit from the introduction of novel genes via the translocation of adult males to the inbred population from a larger population.

The article is currently viewable at:

 http://www.helsinki.fi/ml/ekol/egru/pdf/Madsenetal1999.pdf

I am seeking permission from the copyright holder to reproduce the article in full for the Adder section of the RAUK e-forum.

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Thanks for those caleb, i'll incorporate those into the site as I go along. Some are up on the links page already, some not. RAUK was only born last Saturday.. so give it time to warm up

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As the plough is to a meadow, so Nymphoides peltata is to a pond?

Scary stuff Martin, any news on its spread. I have not seen it in the wild (yet) but have seen pictures of it choking ponds.

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Inbreeding û an overlooked aspect of herpetofauna decline.

For many years I have suspected that isolated populations are suffering from inbreeding depression.

Not only the remnant populations of the glamorous species, such as Sand Lizards and Natterjack Toads, but also increasingly, isolated populations of our more common species.

Observers are reporting that well known populations of the Adder (Vipera berus), are declining at an alarming rate.

The Madsen study¹ in my mind raises a number of important issues for the continued conservation efforts of reptiles and amphibians in the UK.

Firstly, the expected signs of inbreeding associated with domesticated pets are of little consequence. We would not expect polymorphic snakes to survive predation and be extent in the wild. Observation of the Smooth Snake may well show they inhabit small areas today, but clearly individuals do roam if habitat is available, or else they would not have populated the United Kingdom. Madsen points to the true signs of inbreeding depression in wild populations as reduced fertility and survivor-ability of offspring. Difficult factors to measure practically in the field, we may fall back on a study of the genetic variability of the population.

We must all be aware that with changes in farming practice, increased conurbation and general fragmentation of habitat, populations of reptiles and amphibians are very likely to become isolated. It is well established that our native herpetofauna cannot cross the vast tracts of agricultural fields that now form much of our environment. A simple study of changes of land use in ones local area will quickly reveal that many remaining habitats have been isolated for 40 û 100 years. The negative affects of out-breeding depression are surely not a factor, it would seem unlikely that populations of the more common species have adapted to microclimatic differences in this short period.

It is my view that genetic conservation is overlooked at our peril. We may endeavour to save the isolated habitats that remain, but it is of little use if the animals contained within become less and less viable.

I would ask all involved to consider that it is ôpossibleö that a major-factor promoting decline of our native herpetofauna is lack of genetic variability. There are dangers; movement of animals to small populations may carry the risk of promoting disease, invasive plants and the converse effects of out breeding depression. Perhaps the solution lies in the captive breeding of genetically varied stock, perhaps more simply a few isolated areas may be studied and adults from larger populations trans-located and the affects noted.

1) Restoration of an inbred adder population 

 Thomas Madsen, Richard Shine, Mats Olsson, HÕken Wittzell

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Inbreeding depression is usually defined as: a loss of fitness (vitality), characterised by difficulty in conception, increased spontaneous abortion, pre-natal and peri-natal deaths

Inbreeding: is mating between either a close relative, or mating of individuals with at least one common ancestor.

My view on the "visible" signs of inbreeding depression and  the relevance to wild animals is this, if in captivity we breed closely related animals for selective reasons and by choice, for instance to enhance a pair of recessive genes to produce a desired colour ômorphö, the animals are inbred, however the animals may not shown signs of inbreeding depression. There is an increase in the probability that deleterious recessive alleles will come together. Generation over generation the probability increases alarmingly.

In short, inbreeding depression is a danger with selective breeding, but not necessarily the result in the short term.

Considering wild animals, they are not selectively bred to produce colour polymorphism, it is simply that the mating between animals with common ancestors in the population increases the deleterious recessive alleles, leading to a general loss of vitality.

In short, Colour polymorphism maybe a result of inbreeding, it is not however a symptom or sign of inbreeding depression,

 i.e. the population may be normal for colour type, though the gene pairs controlling the phenotype of the population are reduced.

It may be concluded from this, that there are no visible signs in the phenotype of a population that is suffering from inbreeding depression. The animals may appear normal for colour type, but are infact suffering from a loss of vitality - so in answer to one of your questions, waiting for the visible signs will be too late, they will not appear, as there are no visible signs of inbreeding depression. A population can only be said to be free of inbreeding depression if it has good genetic diversity.

If my estimates are right, that many small wild populations have now been isolated for 100 or more years in the UK, the process is advanced and it is likely that ôharmfulö alleles have been reinforced, promoting their decline towards extinction.

In the past these deleterious effects of inbreeding in wild populations were offset by immigration of adult animals carrying novel genes.

It is generally regarded that the species indigenous to the UK were all highly mobile, at least historically, or it is unlikely they would have populated the UK after the last ice period. I fear that the lack of mobility of the Smooth Snake as seen today, maybe a symptom of inbreeding depression, not a reason to dismiss it. I also accept that it maybe due to habitat limitation, I find it difficult to accept it is simply their normal behaviour.

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The Romney Marsh Marsh frogs are a good example of how a population can grow and flourish when it is not faced with habitat limitation. Assuming the founders came from a large population, so were unrelated and 6 were males and 6 were females, the first generation of offspring only had a 1 in 6 chance of mating with a sibling, most second generation mating would be between unrelated animals.  As the frogs are populating new habitats without much competition, the number of adult breeding frogs has rapidly grown and the population will be genetically diverse.

Inbreeding depression comes about in the opposite case when the number of breeding adults is severely limited by habitat constraints. The small population soon becomes closely related and genetic diversity is lost.

(The Marsh Frog was introduced in 1935)

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In Dartford we found a temporary pool, containing vast amounts of spawn. I would be interested in hearing from anyone local to the site as to the usual fate of the tadpoles here, or anyoneÆs experiences of Common Frogs spawning in temporary pools.

I assume the only likely source of nutrients to the developing tadpoles will be each other and that most years the site is not viable?

Common Frog Spawn at Dartford

Site Picture

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Thanks for the advice, I suspected that they stood very little chance in this location. We have contacted Dartford Council and hopefully will hear back next week about permissions to move them to a nearby deeper pond.

There is a problem though, we collected a small sample on Wednesday and this hatched on Thursday, so I am thinking that moving the spawn now is not practical, as many of the young will be motionless in the bottom mud. Could you advise on time scale for the tadpoles to be free swimming and net-able?

The pool is at most 3 centimetres deep and in full sun.

(edited)

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Would be interesting to study first emergences across the country. I can not recall seeing adders this early in the southern regions, so I wonder if they emerge earlier in their northern range to make the most of our poor summers?

The identification pages had 3 or 4 hits for searches of Vipera berus last week so I guess they have been sighted elsewhere.

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We returned today and found the spawn masses in much the state David described, some areas being black with newly hatched tadpoles. The water level had dropped substantially in the last 6 days as shown below. The area is an old clay lined pond that has fallen out of use. We spoke to the Parks Warden for the site and it is hoped that the pond will be repaired within the next few years, it currently leaks into the underlying sand.

Site Picture showing drop in water level

Masses of spawn with hatched young clinging

We collected 200 Litres of spawn from the site, and moved it to the nearest large body of water (approximately 1 mile due east), which we had observed last week to have also been selected by Common Frogs for spawning.

Recipient Site

We observed Smooth Newts and Common Toads spawn at the temporary site today. We will return over the next few weeks to rescue any other tadpoles as the pond dries out. A local volunteer who helped us today mentioned that the three species observed have used the area since the 1940's, but now the pond dries out completely.

Please note: There are many reasons why moving Frogs spawn may be inadvisable, please contact Froglife on Tel: 01986 873733 for advice if you think there is a genuine conservation reason to lift Frogs spawn to another site.

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We moved another 60 Litres of spawn today, many of the tadpoles were stranded in the surrounding mud and we rescued those we could.

20th March showing further drop in water level

We also took a walk around the area to find the woodland pond managed by the same Park Ranger, this area has had attention in recent years, we were very pleased to find masses of frogs spawn here too, so Dartford certainly has a thriving Common Frog population

Woodland Pond

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Hi Cade,

Common Frog Tadpoles

Start by feeding on the leftovers of the spawn they hatch from.

They then move onto green filamentous algae often found growing on aquatic plants.

After a week or so they become omnivorous, eating algae and meat in the form of dead invertebrates such as worms and insects.

Common Toad Tadpoles,

Start the same, but mostly only eat algae until they metamorphose

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Hi JaneW,

Firstly, I was a little surprised Froglife advised you to grow them on yourself, I didn't really consider it an option, but it's not as bad as it might seem!

Firstly, de-oxygenation of the water isn't such a problem in bowls, which have a large surface area, just don't leave them in full sun, and not too many plants as the tadpoles grow larger. It should then be sufficient to top up the water with fresh just to keep the level up in the bowl. The water does not strictly need boiling, standing for 24 hours is sufficient to de-chlorinate the water, I have never had a problem with water straight from the tap with tadpoles of Common Frogs.

On the food issue, they are little eating machines, they will eat anything from dried fish food to dead vertebrates. My own preference is for chopped up earthworms and crickets, as they do not foul the water like fish food, and are a little more natural. (they don't have to be live, dried crickets are available)  They become meat eaters at about 1 - 2 weeks depending on the temperature they are kept at.

With amounts, you will soon see how much they need, as they grow and become free swimming add a few bits of food and see how quickly it goes. Using worms I just add a few chopped up ones and add more when it is all gone.

Your sisters worries are unfounded, the danger of suffocation of the fish is past, this occurs during the spawning frenzy when an adult frog may accidentally grab a fish thinking it to be another frog, your little tadpoles really do not present this risk! (This only occurs very rarely)

If she insists, grow the tadpoles on to little frogs, then they can be released without putting them back in a pond, just somewhere quiet and safe with plenty of cover.

If anyone else has anything to add, I am sure it will be appreciated

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Hi Janew,

Glad I could help. The advice on redleg is translocation no further than 1km from the original pond.

I see no problem at all with you releasing them in the Garden, and why not give them a pond as well! Common Frogs are living in gardens in Central London quite happily. They prefer damp margins of ponds when tiny, but can do quite well far away from water, only seeking a pond when they come to breed at 3-4 years of age. (It might be an idea to sink a bowl of water in the shrubs they can use if they like to begin with, make sure it has some plants and rocks so they can easily climb out.)

If it is any consolation, I've about 300 common frog tadpoles growing on here a few weeks ahead of yours, so any more worries let me know

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