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Individual study: The efficacy of Schwegler chemical repellent in the reduction of Hermann's tortoise Testudo hermanni nest predation at Albera Nature Reserve, Catalonia, Spain

Published source details

Vilardell A., Capalleras X., Budó J., Molist F. & Pons P. (2008) Test of the efficacy of two chemical repellents in the control of Hermann's tortoise nest predation. European Journal of Wildlife Research, 54, 745-748


The western subspecies of Hermann's tortoise, Testudo hermanni hermanni, was formerly widespread in the west Mediterranean region. Due to habitat loss, fires, illegal collecting for the pet trade, road mortality, etc., it has been extirpated from most of its former range. The only remaining native population in Iberia occurs in the Albera mountain range in the Eastern Pyrenees, northern Spain. The survival of the tiny population of tortoises in Albera Nature Reserve is considered threatened by nest predation e.g. in 2005, 48 tortoise nests exhibited signs of predation. The focus of this work was to test the efficacy of two chemical repellents, claimed to be effective in deterring mammalian predators, in order to reduce nest predation. Here, the trail using Schwegler© repellent alone is summarized.

Study area: The study was conducted in Albera Nature Reserve (42°24′40″ N, 3°3′15″ E), Catalonia (Cataluna), northeast Spain. The repellent trialled was Schwegler©, which targets mammalian carnivores; previous studies document that beech marten Martes foina, red fox Vulpes vulpes and genet Genetta genetta are amongst the main tortoise nest predators.

Experimental design: In June (the period of tortoise second clutches) 2006, 128 artificial nests were distributed among eight rectangular 625 m² plots (16 nests/plot) spaced 15 to 20 m apart in an area used by tortoises. Artificial nests were used so as not to imperil tortoise nests. An artificial nest comprised an 8 cm deep x 6 cm diameter hole, three quail Coturnix coturnix eggs were placed inside and the hole was infilled with soil, replicating a natural tortoise nest. Nests were then sprinkled with 15 mL of a solution containing tortoise urine and excrement, simulating female behaviour during nest building. The fluid Schwegler© repellent was applied to a small cotton strip adhered to short wooden strip, and hung by string from branches 15 cm above the ground, following the manufacturer's guidelines for use. These were positioned around the perimeter of four plots 2 m apart (25/plot). The other four plots (no repellent) served as controls.

Monitoring: Nests were regularly visited to determine whether predation had occurred and, on the basis of tracks and other signs, to identify the predator.

All of the artificial nests, regardless of whether protected by repellent or not, were predated after only 4 days. Wild boar Sus scrofa appeared to be the main nest predator.

In response to this failure, a second trial was undertaken in the autumn, for a summary please see:

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