Current Animal Responses to Climate Change

Animals are showing many different types of changes related to climate. These include changes in ranges; abundances; phenology (timing of an event); morphology and physiology; and community composition, biotic interactions, and behavior. Changes are being seen in all different types of taxa, from insects to mammals, and on many of the continents (Price et al. 2000). For example, the ranges of butterflies in Europe and North America have been found to shift poleward and upward in elevation as temperatures have increased (Pollard 1979, Parmesan 1996, Ellis et al. 1997, Parmesan et al. 1999). From 1979 to 1989, population densities of the Puerto Rican coqui (Eleutherodactylus coqui) showed a negative correlation with the longest dry period during the previous year (Stewart 1995). Similarly, the disappearance of the golden toad (Bufo periglenes) and the harlequin frog (Atelopus varius) from Costa Rica's Monteverde Cloud Forest Reserve seemed to be linked to the extremely dry weather associated with the 1986-87 El Nino-Southern Oscillation (Pounds and Crump 1994). Birds' ranges reportedly have extended poleward in Antarctica (Fraser et al. 1992, Emslie et al. 1998), and Europe (Thomas and Lennon 1999). For instance, the northern movement of the spring range of barnacle geese (Branta leucopsis) along the Norwegian coast correlates significantly with an increase in the number of April and May days with temperatures above 6°C (Prop et al. 1998). Reproductive success of the California quail (Calipepla californica) is positively correlated with the previous winter's precipitation (Botsford et al. 1988). Rainfall affects the chemistry of plants eaten by quail, with the plants producing phytoestrogens, compounds similar to hormones that regulate reproduction in birds and mammals. Drought-stunted plants tend to have higher concentrations of these compounds (Leopold et al. 1976). The northern extension of the porcupine's (Erethizon dorsatum) range in central Canada has been associated with a warming-associated poleward shift in the location of tree line (Payette 1987). In the United Kingdom, the dormouse (Muscardinus avellanarius) has disappeared from approximately half of its range over the last 100 years (Bright and Morris 1996). This disappearance appears to be linked to a complex set of factors including climatic changes, fragmentation, and the deterioration and loss of specialized habitat.

Warmer conditions during autumn-spring adversely affect the phenology of some cold-hardy insects. Experimental work on spit-tlebugs (Philaenus spumarius) found that they hatched earlier in winter-warmed (3°C above ambient) grassland plots (Masters et al. 1998). Chorusing behavior in frogs, an indication of breeding activities, appears to be triggered by rain and temperature (Busby and Brecheisen 1997).Two frog species, at their northern range limit in the United Kingdom, spawned 2 to 3 weeks earlier in 1994 than in 1978 (Beebee 1995). Three newt species also showed highly significant trends toward earlier breeding, with the first individuals arriving 5 to 7 weeks earlier over the course of the same study period. This study also examined temperature data, finding strong correlations with average minimum temperature in March and April (negative) and maximum temperature in March (positive) for the two frogs with significant trends, and a strong negative correlation between lateness of pond arrival and average maximum temperature in the month before arrival for the newts. Using less precise methods, a family of naturalists in England recorded the timing of first frog and toad croaks for the period from 1736 to 1947 (Sparks and Carey 1995). The date of spring calling for these amphibians became earlier over time, and was positively correlated with spring temperature, which was positively correlated with year. Changes in phenology or links between phenology and climate have been noted for earlier breeding of some birds in the United Kingdom (Thompson et al. 1986), Germany (Winkel and Hudde 1996, Ludwichowski

1997) and the United States (Brown et al. 1999). Changes in bird migration have also been noted with earlier arrival dates of spring migrants in the United States (Ball 1983), later autumn departure dates in Europe (Bezzel and Jetz 1995), and changes in migratory patterns in Africa (Gatter 1992).

The effect of temperature on the metabolism of dormant horned toads in Brazil was found to be stronger than the effect on resting toads at most temperatures (Bastos and Abe 1998). Reptile physiology is temperature sensitive also. Painted turtles grew larger in warmer years, and during warm sets of years turtles reached sexual maturity faster (Frazer et al. 1993). Physiological effects of temperature can also occur while reptiles are still within their eggs. Leopard geckos (Eublepharis macularius) produced from eggs incubated at a high temperature of 32°C showed reproductive behavioral changes and possible female sterility (Gutzke and Crews 1988). Spring and summer temperatures have been linked to variations in the size of the eggs of the pied flycatcher (Ficedula hypoleuca) (Jarvinen 1996). The early summer mean temperatures explaining approximately 34% of the annual variation in egg size between the years 1975 and 1994. Body mass, which correlates with many life-history traits including reproduction, diet, and size of home ranges of the North American wood rat (Neotoma spp.) has shown a significant decline inversely correlated with a significant increase in temperature over the last 8 years in one arid region of North America (Smith et al. 1998). In studies of spring temperature effects on red deer (Cervus elaphus) in Scotland, juvenile deer grew faster in warm springs leading to increases in adult body size, a trait positively correlated with adult reproductive success. In Norway, red deer born following warm winters (that have more snow) were smaller than those born after cold winters—a difference persisting into adulthood (Post et al. 1997).

Differential responses by species could cause existing animal communities to undergo a reformulation (Root and Schneider 1993). Peach-potato aphids grown on plants kept in elevated CO2 (700 ppm) showed a reduced response to alarm pheromones in comparison to those grown on plants in ambient CO2 (350 ppm) (Awmack et al. 1997a). The aphids were more likely to remain on leaves, rather than move away, in response to the pheromones, possibly making them more susceptible to predators and parasitoids. Temperature and dissolved-oxygen concentrations can alter the behavior of amphibian larvae, and changes in thermal environments can alter the outcome of predator-prey interactions (Moore and Townsend 1998). Climate change may be causing mismatching in the timing of breeding of great tits (Parus major) in the United Kingdom and other species in their communities (Visser et al. 1998). Post et al. (1999) documented a positive correlation between gray wolf (Canis lupus) pack size in winter and snow depth on Isle Royale (U.S.). In years with deeper snow, wolves formed larger packs, which led to more than three times as many moose kills.

0 0

Post a comment