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Tucson, AZ, United States

Ramos-Lara N.,University of Arizona | Koprowski J.L.,University of Arizona | Swann D.E.,Saguaro National Park
Journal of Mammalogy | Year: 2013

Many animals depend on nests for their survival and reproduction, with some species considered obligate tree cavity-nesters. Mearns's squirrel (Tamiasciurus mearnsi) is a species endemic to the Sierra de San Pedro Mártir, Baja California, Mexico, that relies on tree cavities for nesting. Federally listed as threatened in Mexico, and as endangered by the International Union for Conservation of Nature, the ecology of this southernmost Tamiasciurus is poorly known. The aim of this study was to examine the nesting requirements of Mearns's squirrels. We used telemetry to locate the nests and 10-m-radius circular plots to compare habitat characteristics between nest sites and random sites, nest sites of males and females, and nest sites of breeding and nonbreeding females. Nest tree species, nest tree condition, nest tree size (diameter at breast height), canopy cover, and occurrence of white firs (Abies concolor) are important characteristics for nesting. Nest sites of males did not differ from those of females except for nest tree condition. Females apparently do not have specific nesting requirements for rearing young. Unlike other congeners that also build leaf nests and underground burrows for nesting, large trees and snags that facilitate cavity formation are critical for the conservation of this species. © 2013 American Society of Mammalogists.


Wallace J.E.,University of Arizona | Steidl R.J.,University of Arizona | Swann D.E.,Saguaro National Park
Journal of Wildlife Management | Year: 2010

Many aquatic species in the arid southwestern United States are imperiled, persisting primarily in isolated, low-order streams that are increasingly vulnerable to stochastic disturbances. During 2003 and 2004, we surveyed 39 mountain canyons in southeastern Arizona, USA, for lowland leopard frogs (Rana yavapaiensis), a species that has declined in abundance and distribution across its range in the United States. We quantified habitat features at 2 spatial scales, canyon and pool, to identify features that distinguished sites inhabited by frogs from those uninhabited by frogs. Canyons inhabited by frogs had watersheds that averaged 8.1 km2 larger (SE 2.52), pools that averaged 37.8 m3 greater (9.30) in volume, gradients that averaged 4.1 (1.40) less steep, and locations that averaged 3.2 km closer (1.06) to the nearest valley stream than did uninhabited canyons. Plunge pools inhabited by frogs averaged 13.5 (5.66) more perimeter vegetation, 11.2 (5.34) more canopy cover, and 1.9 (0.60) more refuges than uninhabited pools. In general, canyons that provided more perennial water during dry summer months and plunge pools that provided more bank heterogeneity were more likely to be inhabited by frogs. Conservation of lowland leopard frogs and other aquatic species that inhabit xeric systems in the southwestern United States depends principally on maintaining riparian ecosystems that provide habitat for these species and the adjacent uplands that influence the structure and function of these systems. Therefore, both riparian areas and their adjacent uplands must be managed to maintain habitat for organisms that inhabit these rare and diverse ecosystems. © The Wildlife Society.


Zylstra E.R.,University of Arizona | Steidl R.J.,University of Arizona | Swann D.E.,Saguaro National Park
Journal of Wildlife Management | Year: 2010

Effective conservation requires strategies to monitor populations efficiently, which can be especially difficult for rare or elusive species where field surveys require high effort and considerable cost. Populations of many reptiles, including Sonoran desert tortoises (Gopherus agassizii), are challenging to monitor effectively because they are cryptic, they occur at low densities, and their activity is limited both seasonally and daily. We compared efficiency and statistical power of 2 survey methods appropriate for tortoises and other rare vertebrates, line-transect distance sampling and site occupancy. In 2005 and 2006 combined, we surveyed 120 1-km transects to estimate density and 40 3-ha plots 5 times each to estimate occupancy of Sonoran desert tortoises in 2 mountain ranges in southern Arizona, USA. For both mountain ranges combined, we estimated density to be 0.30 adult tortoises/ha (95 CI 0.170.43) and occupancy to be 0.72 (95 CI 0.560.89). For the sampling designs we evaluated, monitoring efforts based on occupancy were 836 more efficient than those based on density, when contrasting only survey effort, and 1730 more efficient when contrasting total effort (surveying, hiking to and from survey locations, and radiotracking). Occupancy had greater statistical power to detect annual declines in the proportion of area occupied than did distance sampling to detect annual declines in density. For example, we estimated that power to detect a 5 annual decline with 10 years of annual sampling was 0.92 (95 CI 0.750.98) for occupancy and 0.43 (95 CI 0.350.52) for distance sampling. Although all sampling methods have limitations, occupancy estimation offers a promising alternative for monitoring populations of rare vertebrates, including tortoises in the Sonoran Desert. © 2010 The Wildlife Society.


Back in 2012, the Grand Canyon National Park began prohibiting the sale of bottled water, in an effort to reduce pollution and cut the costs of waste removal and recycling. Today, over 20 parks have followed suit, and instead provide visitors with free water refilling stations. According to the National Parks Service, using the water stations also reduces the greenhouse gas emissions associated with the production, filling, transportation and recycling of disposable plastic bottles. But the bottled water industry is pushing back, with a small last-minute amendment to a House spending bill. The amendment, introduced by Representative Keith Rothfus, prohibits parks from eliminating “the sale in National Parks of water in disposable plastic bottles.” The Washington Post reports that the industry has spent $510,000 to lobby congress to end the sales bans. Currently, parks that ban the sale of bottled water on their grounds do not prohibit visitors from bringing disposable water bottles into the park. And at many national parks, reusable water bottles are for sale to visitors who might forget to bring their own. The International Bottled Water Association (IBWA), whose members include Danone, Absopure, Grand Springs, Glacier Springs, Evian and about 200 others, argues that banning water sales encourages the consumption of less healthy beverages such as soda. The industry group “applauds” the amendment. “These bans, whether in national parks or college campuses, are misguided attempts to deal with a waste management issue that would be better addressed through efforts to improve recycling rates of all packaged drinks,” said Chris Hogan, IBWA Vice President of Communications, in a press release. Beverage companies have a long history of promoting recycling instead of addressing the problems associated with single-use packaging. Refilling a reusable bottle uses a fraction of the resources compared with recycling many disposable plastic bottles. If banning bottled water does make drinking soda seem like a better option, then perhaps more parks should follow the lead of Saguaro National Park in Arizona by eliminating the sale of both soda and bottled water.


Swann D.E.,Saguaro National Park | Springer A.C.,University of Arizona | O'Brien K.,Saguaro National Park
Park Science | Year: 2011

The Saguaro Census is a long-term monitoring project in Saguaro National Park, Arizona, that features citizen scientist volunteers who learn about ecological change in the park while gathering data on saguaros. In 2010, more than 300 volunteers measured more than 20,000 saguaros. Results of the 2010 Saguaro Census suggest that, after years of decline in at least some areas of the park, the population o this slow-growing, long-lived southwestern cactus species has increased dramatically in recent decades, following the end of a long drought in the 1950s and a warming trend since the 1970s. Citizen science has the potential not only to help parks gather large amounts of data but also to promote greater understanding and communication of natural resources management and climate change science.

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