Tourism at Martillo Island, Tierra del Fuego (Argentina): Are Magellanic penguins (Spheniscus magellanicus) feeling it?

Abstract

Wildlifetourism is increasing all over the world, and its effects may be detrimental to the species involved. Negative effects of human visitation on seabirds may be worse at particularly stressful life stages such as breeding. The current studytook place at Martillo Island, Argentina, where approximately 4000 pairs of Magellanic penguins (Spheniscus magellanicus) breed every year. Twogroups were defined: individuals nesting within 20 meters of the tourist trail(n=27) and individuals not breeding within sight of the tourists (n=54).Breeding adults were sampled during egg incubation (September/October 2017, n=31)and chick rearing in two distinct years with (2017) and without tourismvisitation in 2020 due to the global pandemic (December 2017/January 2017 andJanuary 2020, n=50). A drop of blood was extracted from the tarsal vein andblood smears were made. Smears were fixed with alcohol 70% and dyed with Giemsastain. Leucocyte types (lymphocytes, heterophils, eosinophils, basophils andneutrophils) were identified under optical microscope at x1000. Percentage ofeach cell type was estimated as well as the eosinophil/lymphocyte (E/L) and heterophil/lymphocyte(H/L) ratio as a proxy of immune response to parasites and long-term stress,respectively. For 2017, GLMs were generated with factor (tourism vs. no tourism)and stage (incubation or chick rearing) as fixed effects. Tourism had an effecton all values: higher percentage of heterophils (t=3.18, p<0.05), eosinophils(t=2.76, p<0.05) and heterophil/lymphocyte (t=4.22, p<0.05) and eosinophil/lymphocyte ratios(t=3.45, p<0.05) and lower lymphocyte counts (t= 4.12, p<0.05) than inareas not visited by tourists with no differences between stages (incubation orchick rearing). In 2020, however, there were no differences in physiologicalparameters between birds nesting in areas usually visited vs. not visited bytourists (percentage of heterophils (t=0.96, p=0.34), eosinophils (t=1.00, p=0.32) and lymphocyte counts (t= 0.87, p=0.39),and H/L (t=0.56, p=0.58) and E/L ratios(t=1.07, p=0.29). These results are preliminary as a larger sample is needed overa more extended period of time. However, there seem to be differences inphysiological parameters of individuals exposed or not tourism and theseeffects are reverted once tourism does not occur. In view of these results, questionsrise as to the consequences of growing tourism on the Magellanic penguin colonyat Martillo Island.