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janne
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Posted: 02 Feb 2005 Topic: Pool Frog reintroduction



Concerning the age of esculenta populations in southern Sweden:

1. There are observations in SkÕne (55 N) from at least 1842, in SmÕland (57 N) from the middle of the 1800s, in Ķsterg÷tland (58 N) from the 1800s.
2. Frogs are still numerous in SW SkÕne with thousands of adults in hundreds of ponds covering at least 1000 km2. Most probably this population is linked to the Danish population across Ķresund. Some specimens have even been found near the beach in salt water.
3. The few known populations in eastern SmÕland and Ķsterg÷tland have mostly died out, but one remains in Ķsterg÷tland. This area has the highest summer temperatures in Sweden, explaining records north of the normal area. Extinction is probably connected with ditching, forest change (from leaf trees to needle trees), acidification etc.
4. One newly discovered population in Ķsterg÷tland is probably pure esculenta. Two Swiss biologists currently investigate genetics.
5. Newly discovered localities donĘt necessarily mean that the frogs have been introduced. There are many thousands of ponds and lakes in Sweden and local people normally have no clues regarding different species. I presume introductions are a smaller problem compared with Britain.

Summary: It is highly unlikely that esculenta (and lessonae) in Sweden could be derived from introduction, because of the wide area of localities. In warm postglacial times amphibians and reptiles migrated through Denmark to Sweden and Norway before land areas in between turned into sea. Shells of the turtle Emys orbicularis has been found in bogs up to the north of Ķsterg÷tland (59 degrees N!) which gives an example of how much warmer climate this area experienced at that time. It indicates that green frogs most probably colonised that same areas, got adapted, but only survived at the most favourable localities later when colder weather set in.

Other examples of relict populations in Sweden are the agile frog, separated from the rest of the European distribution by a wide gap, sand lizard up to 61 degrees N and smooth snake up to 62 degrees N. Only in warm localities have these populations survived until recent times.

I donĘt know any archaeological finds of esculenta or lessonae in Sweden.

Best regards

Jan Pr÷jts
Biologist
Lund
Sweden



Janne
janne
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Posted: 03 Feb 2005 Topic: Pool Frog reintroduction



This question is naturally difficult to answer. My guess is that the esculentas have survived since the link to the continent broke up app 6000 BC. They are doing well for the moment and are even expanding their range in SkÕne. In Sweden there have never been any lessonae records together with esculenta that I know of. Ridibunda is lacking. The pure lessonae in Uppland are isolated.

The reason for not finding bone fragments of green frogs in Sweden could depend on acid soils in parts of the country. Emys shells have only been found in Ķsterg÷tland, Ķland and SkÕne, regions dominated by lime bedrock.

Old records of Swedish amphibians and reptiles were collected into one report in 1959 (in English!): GislŚn, T. & Kauri, H. 1959. Zoogeography of the Swedish amphibians and reptiles, with notes on their growth and ecology. Acta Vertebratica 1: 191-397. Not on Internet unfortunately.

Find records of esculenta in NRM: http://www2.nrm.se/ve/herp/herpwais.shtml.en

Link to ōSpecies observations netö: http://www.kristianstad.snf.se/arter/art.htm
Deals mostly with amphibians in SkÕne. Only in Swedish. Photos of greens frogs can be found in april 2002, june 2002 and july 2004.




Janne
janne
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Posted: 15 Feb 2005 Topic: Pool Frog reintroduction



As I have stated earlier, there is much to support the idea of natural origins of esculenta in Sweden and not much of the opposite:

? Old records from many places in a large area. How can these all have sprung from introductions?
? Only few records mention specifically introduction of frogs, only one dubious (nothing written) talk of frogs from the continent. It should also be difficult for any continental frog to adapt and survive in northern climates and biotopes. One case that I know of talks of accidental esculenta in a fish farm (200 m above sea level). Only tadpoles were collected in the autumn because climate was too cold. No grown frogs have been found in this locality.
? Natural distribution in the Baltics (includes esculenta, ridibunda and lessonae), where all three reaches well into Estonia, with a climate not unlike southern Sweden. When you look at the distribution maps the Swedish populations doesnĘt look out of place at all.

One explanation for remaining northern pool frogs in Sweden could be land elevation, which in the Uppsala area is about 6 mm/year. This process clearly produces new habitats along the coast which enables this metapopulation to colonise new ponds and small islands (some rather remote) in a sea not very salty (the importance of early succession have been mentioned earlier in this forum). In the south of Sweden land elevation is much lower (or even inverted) which could explain lesser chances of survival in the long run for this species.



Janne
janne
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Posted: 16 Feb 2005 Topic: Pool Frog reintroduction



Swedish old records

Most are collected in the above-mentioned GislŚn and Kauri1959. Some records are from different museum collections, some from LITERATURE and some from personal communication. Most records are from the 1900?s. To save time I have only listed records before 1900.

SkÕne (SW corner): Lindved, Gothenburg Natural Museum 1841, Fjõllfotasj÷n NILSSON 1842, Yddingen NILSSON 1842, Genarp, NILSSON 1842. There is also a now lost frog in Lund Zoological Museum from 1844 collected in NE part of the county.

SmÕland, Kalmar lõn: Kyrkebo bõck, Uppsala Zoological Museum 1863. Tveta and M÷rlunda, Natural History Museum in Stockholm 1854, WETTERBERG 1864. I have copied the last reference. In the article this author states that he has seen numerous green frogs in ponds near EmÕn River between 1842 and 1864.

Ķsterg÷tland, Gusum: Lund Zoological Museum 1855, Natural History Museum in Stockholm 1862, NILSSON 1842.

Comment 1:
As you can see, most old records are from museums. NILSSON 1842 is one of the oldest popular books in zoology in Sweden (Nilsson, S. Scandinavisk Fauna 3. Amphibierna. 119 pp. Lund). When considering old records one must remember that knowledge of different species in Sweden didnĘt evolve before Linnaeus in the 1700?s. And the above-mentioned publication was the first step for most common people to learn about the Swedish fauna, which explains why there are no records before that.

I can fax the whole esculenta chapter from GislŚn and Kauri if anyone is interested.

Comment 2: I have deliberately not gotten into the specific discussion concerning introduction of Swedish lessonae to England.

In the 80?s Bombina bombina was reintroduced as Danish tadpoles after this species died out in Sweden. It took several efforts, but today Bombina has reached over the threshold number and is spreading by itself in the landscape. Danish and Swedish stock has been regarded as close relatives.

Best regards





Janne
janne
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Posted: 23 Feb 2005 Topic: Pool Frog reintroduction



I have some final questions to John A Burton:

1. Why is it important to know if thereĘs any Swedish records from Linneus time (1700Ęs), when you indirectly suggest that introduction could have taken place before that? What is the big difference between 1700Ęs and 1800Ęs? Earlier than Linneus there simply didnĘt exist any frog recorders in Sweden!

Below you can fŻnd a link to a Rana esculenta from Linneus time (I found it today):

http://www.ebc.uu.se:8080/onlineCollection/showDetail.do?id=136&topCategory=1

You also have overlooked the possibity of introduction with animals from natural localities already existing in the country.

2. Then, where is the actual natural northern boundary in Europe? Denmark? Germany?

3. What could have STOPPED natural spreading through Denmark and Sweden (and England) in a post glacial climate 2-3 degrees warmer than today? Obviosuly not climate, proven by modern distribution.

You wrote: ōThe present distribution of lessonae, ridibunda and esculenta, in the Baltic region, in common with many other parts of Europe, shows indications of being modified as a result of human translocations.ö

What are these indications regarding the Baltics?

No, I?m still fully convinced that esculenta and lessonae are a natural ingredient in the Swedish fauna, because of distribution og Hyla, Pelobates, Bombina and other warm loving amphibians in the same area. And shells of Emys is another proof of that. To my knowledge, there is no place in Europe where Emys reaches farther north than esculenta. The esculenta and lessonae northern range should be regarded as leftover after a long period of post glacial decline due to colder weather and changes in forests and water chemistry. As much as one can overrate human influence, one can easily underrate the frogs own ablity to migrate, a totally natural behaviour in forever changing landscapes and climates.

Best regards





Janne
janne
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Posted: 23 Feb 2005 Topic: Pool Frog reintroduction



Unfortunately, I don't know.

When Linneus travelled in SkÕne in 1749, he only mentioned Bombina bombina specifically, and its curious bell-sound. In one location at midsummer he also mentioned croaking frogs "like ducks" and "not like the normal frogs", which most people have interpreted as the tree frog, which inhabits the same area today. But perhaps it was green frogs instead.


Janne
janne
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Posted: 18 May 2005 Topic: Sweden update



Our amphibians have been active for some time now and last species to begin mating was Rana esculenta, which recently started croaking.

In summary, we have slightly increasing populations of rare species in the southern province of SkÕne. There you can find all amphibians that occur in Sweden, except Rana lessonae. For example, reintroduced Bombina bombina is reaching at least 3000 adults and spreading. Hyla arborea 20 000, Rana esculenta 20 000, Pelobates fuscus 2000, Bufo calamita 1000 and Bufo viridis 500 (app. numbers). The situation for Bv is in focus, with efforts to reintroduce it to new suitable localities. This is done through pond digging and tadpole/toadlet introduction. On one locality we have just discovered a successful mating pair (öAsk and Emblaö) from the introductions, the first of itĘs kind! In the small pond we had at the same time Triturus vulgaris, T. cristatus, Hyla arborea, Pelobates fuscus, Rana dalmatina, Rana temporaria, Bufo bufo and Bufo calamita (reintroduced), altogether 9 species. Missing was Rana arvalis. Bombina and Esculenta lacks on this locality.

ItĘs getting better..

Best regards



Janne
janne
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Posted: 19 May 2005 Topic: Sweden update



The richness of species in south SkÕne depends on mild climate, together with a varied landscape with leafy woods, grazing areas, shore meadows and natural ponds (ödeath-ice holesö). At the same time it is a densely populated area, dominated by agriculture and urban areas, which for example has caused a reduction of Pelobates numbers of 95 % since 1960! Only in the last years conservation efforts have increased the numbers of adults and localities again.

In Sweden we have the same six reptiles as in England and you can find them in SkÕne. Sand lizard is found in many localities, but Coronella only seldom in the east of the province, mostly in rocky areas as in the rest of the country. So it is not found in pure heath land as in England. Blekinge and Ķland to the east of SkÕne has many good localities for the smooth snake.

So in summary, best between april 15 and may 15, is is possible in a rather short radius (50 km in each direction) find altogheter 18 species! And öallemansrõttenö makes it possible to walk on every non-arable och non-garden land and at least see protected species.

A link to pictures http://www.jakobaxelsson.se/images.html

Best regards



Janne
janne
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Posted: 19 May 2005 Topic: Sweden update



Yes, but I have not seen one myself. On Gotland there is a subspecies which sometimes is totally black.

Pictures:

http://www.sthlm-herp.net/shf/index.html

http://www.i.lst.se/i/amnen/Naturvard/fridlysta_vaxter_djur/djur/gotlandssnok.htm


Janne
janne
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Posted: 20 Jun 2005 Topic: Sweden update



Anyone interested in green frogs of northern Europe can look at recent TV pics from Sweden (in Swedish). Real player needed.

In Ķsterg÷tland at Hannõs (N 58 10, E 16 20), there exists a mixed population of esculenta and lessonae frogs, therefore unique to Sweden! Otherwise the two forms are separated in different areas. Genetics and origins are not yet solved at this locality, but studied by Christian Jakob and Martina Arioli in Switzerland. Only diploid esculenta here. Currently there are between 50 and 100 adults in the main pond, the rest in the nearby lake Vindommen:

http://svt.se/svt/road/Classic/shared/mediacenter/player.jsp?d=33745&a=404044


By the coast in Uppland lessonae is breeding in many ponds and are doing quite well for the moment:

http://www.tv4.se/bredband/category.aspx?treeId=100711&pid=14108

Best regards



Janne
janne
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Posted: 15 Jan 2006 Topic: Pool frogs to be reintroduced today



Hi there!

Does anybody know how the introduced pool frogs reacted in
their new environment? Dealing with introduction of other
species in Sweden, it seems that many animals (juveniles and
adults) tend to emigrate from the introduction pond and are not
seen again. But some stay behind and begin mating.

Best regards



Janne
janne
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Posted: 27 Oct 2006 Topic: Smooth snake inventory in Sweden



I need some good advice on how to start a smooth snake
inventory at Stenshuvud national park in SkÕne province in
Sweden. The area in question contains a very mixed
landscape with cliffs, heath, leaf tree forests and bushy areas.
All six swedish reptiles are found here but observations of the
smooth snake, typically, are rare.

The idea was to use a number of plates/tins in some parts of
the park to make it easier to find the snakes. Questions:

how many tins is minimum?
which is the ideal material?
how long does is take before the snakes normally discover the
tins?
is there any published data on a specialized inventory in
England?

More info on Stenshuvud:

http://www.m.lst.se/skane/index.cfm?page=D02F7C38-9A39-
8B3F-283BC596977C1F49

Kind regards

Jan Pr÷jts


Janne
janne
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Posted: 28 Oct 2006 Topic: Smooth snake inventory in Sweden



Thanks.

I have little knowledge off adders on the islands, except that
there are adders on both Ķland and Gotland, together with the
two other species. Fairly isolated smaller islands in the
Stockholm archipelago also have adders.

One article deals with adders on islands:
http://links.jstor.org/sici?sici=0021-
8790(199102)60%3A1%3C253%3AVISSDA%3E2.0.CO%3B2
-B
This one is from Hallands Võder÷ on the west coast:
http://md1.csa.com/partners/viewrecord.php?requester=gs&
collection=ENV&recid=1811440&q=&uid=786848307&
setcookie=yes

Regards




Janne

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