Individual study: The efficacy of Schwegler Stop and Jabal chemical repellents in the reduction of Hermann's tortoise Testudo hermanni nest predation at Albera Nature Reserve, Catalonia, Spain
Vilardell A., Capalleras X., BudÃ³ 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 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, a trial using a combination of two commercially available repellents (Schwegler© and Stop Jabalí©), is summarized; this was undertaken in response to results of an earlier trial using Schwegler© repellent alone (for a summary see: www.conservationevidence.com/ViewEntry.asp?ID=1365) which proved ineffective.
Study area: The study was conducted in Albera Nature Reserve (42°24′40″ N, 3°3′15″ E), Catalonia (Cataluna), northeast Spain. The two repellents trialled were Schwegler©, a mammal carnivore repellent (studies indicate that beech marten Martes foina, red fox Vulpes vulpes and genet Genetta genetta are amongst the main tortoise nest predators); and Stop Jabalí© (Hagopur GmbH) a specific repellent for wild boar Sus scrofa (found to be the main nest predator in the earlier trial).
Experimental design: In September (the tortoise hatching season) 2006, 160 artificial nests were distributed among eight 625 m² plots (20 nests/plot) 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). Additionally, aluminium strips containing Stop Jabalí©, were hung on branches 1 m above the ground and 3 m apart around the plot perimeters, again according to the manufacturer's guidelines. 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.
In comparison with the earlier trial using Schwegler© repellent alone, in which all nests were predated within four days (mostly by wild boar), the only noticeable effect of the combination of repellents was to delay predation, although after 4 days almost all nests in plots protected by the repellents had been predated. The authors concluded that the repellents trialled were unsatisfactory for reducing nest predation.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.springerlink.com/content/a827582202062651/fulltext.pdf