Inventory & Monitoring

U.S. Fish and Wildlife Service policy directs refuges to use the best available science to conserve wildlife and their habitats, including methods for monitoring fish and wildlife populations. Aransas National Wildlife Refuge is doing this by applying the best science available to not only estimate how many whooping cranes are on the wintering grounds, but to also better understand the habitats they prefer.

  • Whooping Crane Winter Abundance


    This protocol is the first complete, peer-reviewed site-specific protocol (nation-wide) for the Inventory and Monitoring initiative within the National Wildlife Refuge System. It specifies the process that will now be used to estimate population abundance at the refuge during the winter season. For best results, open the link below using Acrobat X or Adobe Reader X (or a later version).

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  • Historical Aerial Survey Dataset

    Whooping Cranes

    The Aransas-Wood Buffalo population of whooping cranes (Grus americana) declined to near extinction by the 1940s. Starting in winter 1950-1951, annual aerial surveys were conducted to observe and record the number of whooping cranes wintering on the refuge and surrounding areas. This effort resulted in 38,332 observations of whooping crane groups being marked on paper maps between winter 1950-1951 and winter 2010-2011. U.S. Fish and Wildlife Service staff recently digitized those locations and archived them in single file, which is available for download.  These data are freely available to the public, but we caution that these data have quality issues and limitations (see documentation for additional details).

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  • Blue Crab Abundance


    Blue crabs are an important food source for over-wintering whooping cranes at Aransas National Wildlife Refuge. Understanding the relationship between whooping cranes and blue crabs is important.

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  • Wolfberry Production


    Whooping cranes depend on wolfberry early in the winter as a food source to regain energy after their long journey to the refuge for the winter. It is important for refuge managers to understand the impact of drought on berry production.

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