conservation.arizona.edu - invasive species

Palmer, G. H., J. L, Koprowski, and T. Pernas. 2008. Tree squirrels as invasive species: conservation and management implications. Pp 273 - 282 in G. L. Witmer, W. C. Pitt, K.A. Fagerstone (eds.), Managing vertebrate invasive species: proceedings of an in

thackerk1 — Wed, 24 Jul 2019 22:02:20 +0000

Authors

Geoffrey H. Palmer

John L. Koprowski

Tony Pernas

The impact of invasive species on native biodiversity is increasing worldwide. Mammalian invaders are formidable ecological and economic threats, and tree squirrels are models of such challenges. We review the worldwide distribution of tree squirrel introductions and detail their nearly universal success. The biological characteristics of tree squirrels that enable success as invasive species are: high reproductive potential, high vagility, diverse food habits, ability to construct nests, and plasticity in human-impacted landscapes. We document costs and benefits of tree squirrel introductions, and discuss existing management strategies planned for some species. We focus on an introduced population of Mexican red-bellied squirrels (Sciurus aureogaster) found in Biscayne National Park, Florida, United States. Originally introduced to Elliot Key in 1938, the population expanded until Hurricane Andrew in 1992. Thought to be extirpated, recent sightings initiated a project to assess status and distribution within the Park. A field study has provided valuable information on potential and realized impacts that the squirrel population has on the native ecosystem that includes several species of conservation concern. Management strategies for Mexican red-bellied squirrels can be formed after research to develop prudent and effective means to meet the challenges that result from control measures to deal with this exotic species.

Additional Information

TREE SQUIRRELS AS INVASIVE SPECIES: CONSERVATION AND MANAGEMENT IMPLICA TIONS

Date of publication:

2007

Topics

invasive species

red-bellied squirrels

tree squirrel

management strategies

Palmer, G. H., J. L. Koprowski, and A. J. Pernas. 2013. Nest tree and site selection of an introduced population of red-bellied squirrels (Sciurus aureogaster). Journal of Mammalogy 94:1274-1281.

thackerk1 — Wed, 24 Jul 2019 21:30:22 +0000

Authors

Geoffrey H. Palmer

John L. Koprowski

Anthony J. Pernas

Nests play a crucial role in the life history of tree squirrels, and can be a critical component of their biology that enables them to be a successful invasive species. Red-bellied squirrels (Sciurus aureogaster) were introduced to Elliott Key, Florida, in the late 1930s, and spread to nearby islands. Red-bellied squirrels were believed extirpated by Hurricane Andrew in 1992, but were rediscovered on Elliott Key in 2005. In 2006 and 2007, we surveyed for squirrel nests and measured vegetation to evaluate forest characteristics associated with nest-site selection by squirrels, and compared these data to measurements collected at random locations. Squirrels placed nests in large trees with more canopy linkages in mixed-hardwood forest, and the nest trees were in areas with large trees, high tree density and canopy cover, and lower recent hurricane damage. Red-bellied squirrels selected characteristics of nest trees and forest structure in similar ways to individuals in their native range, and to other species of tree squirrels in general. Results from our research allowed land managers to assess possible management actions and provided important information for them to develop an effective management strategy. Park officials are currently working toward complete eradication of the introduced population of red-bellied squirrels from the Florida Keys. We suggest that behaviors of individuals in native ranges may elucidate patterns for individuals introduced to novel environments; however, we also caution that care must be taken in further extrapolation. Our findings emphasize the importance of understanding ecology of introduced species for effective management.

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Nest tree and site selection of an introduced population of red-bellied squirrels (Sciurus aureogaster)

Date of publication:

2013

Topics

habitat selection

invasive species

Mexican gray squirrel

nesting behavior

species eradication

tree squirrel

red-bellied squirrels

Biscayne National Park

Palmer, G. H., J. L. Koprowski, and A. J. Pernas. 2014. Distribution and spread of an introduced insular population of red-bellied squirrels (Sciurus aureogaster) in Florida. Mammalia 78: 67-73

thackerk1 — Wed, 24 Jul 2019 21:24:17 +0000

Authors

Geoffrey H. Palmer

John L. Koprowski

Anthony J. Pernas

Introduced populations of species pose one of the greatest threats to the persistence of native species. Documentation of distribution, range expansion and habitat use of introduced populations are key components of developing effective management strategies for the control and eradication of invasive species. In 2006 and 2007, we surveyed four islands in Biscayne National Park for nests to evaluate the presence of red-bellied squirrels (Sciurus aureogaster) and the distribution and index of dispersion of their nests in the Florida Keys archipelago within the Atlantic Ocean. Red-bellied squirrels were initially introduced to Elliott Key, Florida, USA in in 1938. We documented evidence of squirrels on two additional islands, Sands Key and Old Rhodes Key, which adds to concerns of spread of this introduced squirrel to areas with endangered endemic insular mammals. Squirrel nests were documented only in mixed-hardwood forest, and nests had a clumped distribution within this forest type. Range expansion was a chief concern to the National Park Service, as continued spread could result in squirrels exiting the park, and prompted management action. Understanding nest site selection and distribution was critical for developing an eradication strategy for the introduced population of red-bellied squirrels from south Florida.

Additional Information

Distribution and spread of an introduced insular population of red-bellied squirrels (Sciurus aureogaster) in Florida

Date of publication:

2014

Topics

colonization

habitat selection

invasive species

red-bellied squirrels

species eradication

Minor, R. L. and J. L. Koprowski. 2015. Seed removal increased by scramble competition with an invasive species. PLoS ONE 10:e0143927. doi:10.1371/journal.pone.0143927

thackerk1 — Tue, 23 Jul 2019 23:40:28 +0000

Authors

Rebecca L. Minor

John L. Koprowski

Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert’s squirrels (Sciurus aberti) on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), which consumes similar foods. In the presence of invasive Abert’s squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert’s squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert’s squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert’s squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure.

Additional Information

Seed Removal Increased by Scramble Competition with an Invasive Species

Date of publication:

2015

Topics

Mount Graham Red Squirrel

Abert’s squirrel

competition

invasive species

seed removal

History and current status of invasive nutria and common muskrat in Korea

thackerk1 — Mon, 22 Jul 2019 21:16:30 +0000

Authors

Yeong-Seok Jo

Jonathan J. Debridge

John T. Baccus

Nutria, or coypu (Myocastor coypus), were introduced to South Korea in 1985 and became an invasive species in the late 1990s. Despite being limited to the Nacdong River system, the nutria population is well established there. The common muskrat (Ondatra zibethicus) invaded North Korea via the Russian and Chinese borders during the 1960s, but the species is still confined to the extreme northeastern portion. In South Korea, muskrats were introduced in 2005. Although muskrat farms are not commercially viable, they have increased. Since 2009, local and federal governments have tried to remove nutria using trappers and bounty hunting. From 2011 to 2015, 11,258 nutrias were removed but a sustainable population still exists. Although complete nutria removal has been achieved in other countries, the eradication campaign in South Korea has not been strictly modeled on these successes. Despite the concern about muskrats, prevention against their possible release has never been implemented. We present the history of nutria and muskrat in Korea and examine the current eradication projects. We propose that unified science- based eradication strategies would be the most likely to succeed, and urge the South Korean government to initiate management designed to avert potentially harmful ecosystem effects of invasive muskrats.

Additional Information

Wetlands DOI 10.1007/s13157-016-0867-z.

Date of publication:

2016

Topics

invasive species

Korea

muskrat

Nutria

eradication

Research Categories

Invasive Species Natural History

Differential response to fire by an introduced and an endemic species complicates endangered species conservation

thackerk1 — Thu, 27 Jun 2019 22:58:10 +0000

Authors

R. Nathan Gwinn

John L. Koprowski

Fire is a natural component of, and serves as a tool for, the restoration of forested ecosystems worldwide; however, disturbance due to fire also has been implicated in the proliferation of invasive species. How these fires affect occupancy and use of the forest by wildlife is of great concern, in particular, the differential response of non-native and native species. In the North American Southwest, prior to European settlement, frequent wildfires helped to maintain forest structure. We examined the effect of a large wildfire on an introduced population of the Abert’s squirrel (Sciurus aberti) that has invaded the high elevation forests inhabited by the critically endangered Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis). We found that introduced Abert’s squirrels were more common than native red squirrels in burned areas. Abert’s squirrels did not abandon burned areas but nested, foraged, and did not adjust their home range size in burned areas. This suggests that invasive Abert’s squirrels are better able to exploit burned areas than native red squirrels and that fire can favor non-native species. This interaction between non-native species, native species, and fire adds new insight into the complexities of conservation and restoration of ecosystems and helps to inform conservation activities worldwide.

Additional Information

Hystrix

Date of publication:

2016

Topics

Mount Graham Red Squirrel

Abert’s squirrels

non-native species

invasive species

fire

Research Categories

Disturbance Ecology Sky Islands Spatial Ecology Threatened and Endangered Species