Snakes are already present all over Ibiza due to human mobility

An expansion that was already foreseen, but that the technician of the Consortium for the Recovery of the Fauna of the Balearic Islands (Cofib), Victor Colomar, considers that it is too accelerated to be natural. That is why he believes that they could be moving by human means. A hypothesis difficult to confirm with reliable data, but it seems the most likely theory.

These are some of the assessments made by Colomar at the halfway point of the 2022 campaign to control the snake population in the Pitiusas.

Increase of captures

So far this year, Cofib has 1,600 captures in Ibiza, to which should be added the 500 captures of the hunters' association and there is still no data from the campaign 'Sargantanes o Serps' promoted by Gen-Gob and Amics de la Terra. In any case they would be many more catches than at this point in previous years.

In Formentera 400 captures have been reached, data that would be within the forecasts.

Colomar expresses concern for the largest of the Pitiusas, due to the aforementioned presence of snakes throughout the island and the fact that in half of it there is a high density. The areas of Sant Joan, Santa Eulària, Roca Llisa and the periphery of Jesus to Ibiza would be the areas with high density detected on the island.

The northeastern fringe of the island was the first affected by the arrival of snakes due to the importation of olive trees and it can be seen how the settled population goes down towards the south until it has settled in the surroundings of Vila. «Especially in Sant Joan and the periphery of Jesús and Vila the density is particularly high,» Colomar explained. In particular, the peripheral area of Vila stands out, where between last year and this year there has been an incredible change in density.

Each passing year is a new situation as we know better what the expansion pattern of the species is. «In the 2016-2018 season we could only theorize about how they were expanding. Now that we are starting to detect patterns we are surprised by the population explosions of snakes in areas where we appreciate an explosive population increase. There are areas where the opposite is happening in a way that is still unexplained».

These are data that give the technicians advantages to combat invasive species, but are difficult to obtain, given that the conclusions on the expansion are obtained from the observation of long periods of time.

Strategy

In addition to the usual means, this year there has been an increase in the number of traps and personnel through the Sustainable Tourism Tax, which means that Cofib technicians are managing an average of 1,200 traps, with the possibility of increasing this number throughout the year in Ibiza.

Regarding the use of the traps, Colomar explains that Cofib has around 2,000 cages that are on the move and in a continuous process of activation and removal. With this, Colomar indicates that the average number of active traps will increase over the coming weeks. In Formentera there are 400 stabilized traps, which make up the effective control perimeter.

According to the density pattern, in the case of Ibiza, the traps are being moved and reorganized. «Now, in the middle of the campaign, we redefine objectives. We remove traps from some sites and place them in others, so that the average number of traps remains stable but the number of trapping points increases», explains the technician.

Formentera

In Formentera the snake population is still confined to the area of La Mola, with some occasional sightings in low areas, something within normality. The Cofib technician indicated that it is possible that there are occasional sightings of snakes in other areas of the island, but that it is not something to worry about. However, he is optimistic about eradication, without being able to give dates.

Colomar points out that the strategy is being effective but the population is being «very resistant to trapping». Many captures are carried out constantly, but in spite of this the population remains stable. «It is something we could not know, there is no history of this type of strategies and campaigns and we cannot know how long they will last. It surprises their resistance but the good prospects remain because they have not left the established cordon of traps».