View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Biol Invasions (2010) 12:1909–1922 DOI 10.1007/s10530-009-9618-x PERPECTIVE AND PARADIGM Exotic deer in southern Latin America: what do we know about impacts on native deer and on ecosystems? Werner T. Flueck Received: 17 June 2009 / Accepted: 10 October 2009 / Published online: 23 October 2009 Ó Springer Science+Business Media B.V. 2009 Abstract A recent review on exotic cervids con- habitat where the food item of supposed major cluded that deer introduced to Patagonia impacted overlap was absent, and suggesting that red deer habitat and native huemul deer Hippocamelus bisul- might cause exploitation competition was not sup- cus. I evaluate these assertions and amend informa- ported by cited data. There was no mention that tion about this South American case study. huemul are foremost exposed to livestock rather than Categorizing deer along narrow characteristics may exotic deer. Concluding that exotic prey including red be too restrictive to allow accurate predictions about deer increase predator density resulting in increased interactions. More effective is considering the mag- predation of huemul (apparent competition), was not nitude of plasticity (behavioral, phenotypic, genetic). supported by cited studies. To the contrary, high- The dichotomy of native versus exotic deer masks density puma (Puma concolor) could not prevent situations where prevailing ecological conditions are guanaco (Lama guanicoe) from increasing [13-fold, far from ‘native’, such as absence of predators, and nor that huemul expanded into these sites. Not only such results from artificial settings have limitations. were those studies opposite to conclusions in the Studies used to contrast effects on vegetation from review, but none had studied huemul nor predator exotic red deer (Cervus elaphus) versus native population trends. Data from little known species like huemul did not analyze native deer and provided no huemul should be used with reservations when data to support conclusions in the review. Huemul aiming at generalizations. were concluded to have high trophic overlap with red deer whose diet, however, was determined in another Keywords Invasion Á Cervus elaphus Á Introduction Á Argentina Á Alien Á Exotic Á Invasive species Á Hippocamelus bisulcus Á W. T. Flueck Dietary overlap Á Habitat impacts Á National Council for Scientific Research, Interspecific competition C.C. 176, 8400 Bariloche, Argentina W. T. Flueck (&) Institute of Natural Resources Analysis, Universidad Atlantida Argentina, Mar del Plata, Argentina Introduction e-mail: [email protected] Translocations and introductions of cervids to novel W. T. Flueck Swiss Tropical Institute, University Basel, regions date back at least to Phoenician sailors who Basel, Switzerland introduced fallow deer (Dama dama) to locations 123 1910 W. T. Flueck around the Mediterranean (Masseti and Mertzanidou provided by D&W on their case from South America 2008). Romans followed by bringing fallow deer to about exotic deer impacting native deer, and to show northern Europe, and in the 10th century Normans that information available on poorly known species introduced the same to Britain. Since that time, with should be used with due reservations when making all continents having received exotic cervids, much generalizations. Although D&W used the cold-tem- information has accumulated about such liberations. perate huemul (Hippocamelus bisulcus) to illustrate Introductions have occurred under many different their main arguments, Flueck and Smith-Flueck settings: New Zealand (NZ) lacked native terrestrial (2006a) pointed out that even basic information on mammals (except bats) and Australia lacked euthe- this species and on most of its subpopulations is very rian herbivores; Saint George’s island lacked native scarce, having found only nine original studies on a herbivores and large predators; while other regions Cross-Search of ISI Web-of-Knowledge and 17 contained either native cervids and large predators, or external databases (1945–2006). Additional informa- native cervids with large predators already extermi- tion on huemul from grey literature and unpublished nated (Lever 1985; Leader-Williams 1988; King reports has been summarized by Diaz and Smith- 1990). Although a few introductions involved only Flueck (2000), but was not included in the review by one cervid, most cases involved mixtures of intro- D&W. Among fundamental needed conservation duced ruminants, including domestic ones, some of actions, IUCN thus recommended increasing well- which became feral. The subsequent population founded knowledge on the ecology and biology of dynamics of a given introduced cervid and their huemul and factors preventing its recovery (Jime´nez environmental impacts resulted thus in many differ- et al. 2008). ent outcomes. There are inherent problems when reviewing such complex multifactorial biological interactions on a global scale in search of general- The utility of categorizing cervids along narrow izations. For one, limited data results in tradeoffs ecological criteria between providing a reasonable number of examples and using examples with well-founded conclusions. Categorizing cervids based on their ecological char- Although generalizations about impacts of exotic on acteristics allows predictions of interactions, and native cervids and ecosystems are a promising avenue therefore, the possibility to anticipate degrees of in search of management recommendations, it is impact from an exotic deer on native ones or on misfortunate when emphasis is placed on examples of ecosystem components. The accuracy and value of poorly known species which thus have many basic such predictions are linked directly to the precision of biological and ecological issues pending to be characterizing ecological attributes of interacting understood. Reliance on weak sources of information species. For instance, if a native deer is a strict can lead to increased variation when making gener- concentrate selector, but the exotic deer is a strict alizations, and if erroneous, will likely perpetuate grazer, one can assume that there is little impact from dogmas based on outdated or wrong information the exotic species, at least in terms of diet. Nonethe- about the focal species used for the analysis. less, the most important attributes are related to the In this paper I analyze evidence put forth by variance in all biological responses (intraspecific Dolman and Wa¨ber (2008, D&W) in their review of variation) that a given species is able to express (e.g. impacts of exotic deer on native deer and their West-Eberhard 1989). This plasticity has different ecosystems where they used examples from Europe, origins, such as behavioral, phenotypic, or genetic. South America, Australia and NZ in an attempt to Fallow deer, for instance, respond differently accord- find general global patterns and to reveal the scale of ing to environmental settings. When sympatric with such detrimental impacts. I will address the utility of other cervids in a modified environment (e.g. enclo- categorizing cervids along narrow ecological criteria, sures or feeding stations) lacking a large predator the dichotomy of native versus exotic deer, the community, they were effective competitors, as impact of exotic deer on forests, and the existence of reviewed by D&W. Yet though widely introduced exploitation and apparent competition. My other in Patagonia, they remain in low numbers compared objectives are to add to and amend information to red deer (Cervus elaphus), guanaco (Lama 123 Exotic deer in southern Latin America 1911 guanicoe) and livestock. Possibly their lack of extinct. Thus, characteristics of subsequent popula- defenses against native predators is preventing a tion dynamics of this red deer population with their stronger population growth rate. Even well studied environmental impacts and behavioral patterns deer continue to surprise us with their repertoire of resulted not from an evolutionarily intact setting, possible responses: who anticipated a red deer female but rather from an artificial one (Haller 2002). capable of driving a Patagonian puma (Puma con- Besides affecting prey mortality rates, predators have color)—a hungry female with a cub—up a tree an important role through nonconsumptive effects in (Flueck 2004)? Meanwhile lesser-known species, like structuring ecological communities (Flueck 2000; huemul, are unknown with respect to their plasticity Pierce et al. 2004). Nonlethal effects on prey include (Diaz and Smith-Flueck 2000). reducing their activity times, altering their habitat The frequently used classification of species use, increasing their group size, or changing their according to major patterns has inherent limitations. vigilance levels, which on a population level may For instance, dietary patterns of reindeer (Rangifer actually be more important than lethal effects tarandus) from Saint George island, Svalbards, or (Altendorf et al. 2001; Pyare and Berger 2003; Creel Alaska differ substantially, and reindeer have large and Christianson 2008). Study results from artificial intraspecific variations creating a continuum from and ecologically incomplete settings thus have their selective feeding to generalist feeding behavior (Sko- limitations. gland 1984). Similarly, mule deer (O. hemionus)or D&W misapplied the term keystone to overabun- white-tailed deer (O. virginianus) occur from high dant deer. They did not distinguish