Schmidt, Jason Alan (2009-12). Population Status and Evaluation of Landscape Change for the Lower Keys Marsh Rabbit. Master's Thesis. Thesis uri icon

abstract

  • Wildlife biologists and land managers tasked with the recovery of the endangered Lower Keys marsh rabbit (LKMR; Sylvilagus palustris hefneri) were in need of a current population estimate as well as a method to estimate the LKMR population annually. Habitat loss and fragmentation from population growth and development have threatened the existence of the LKMR. Establishing and understanding long-term habitat availability for the LKMR is important for determining causes of historical population declines as well as designing and implementing successful recovery plans. I conducted a range-wide pellet survey and a mark-recapture study to estimate the LKMR population. I evaluated the fit of 5 models and considered the variation in behavioral response model the best model. I correlated (r2 = 0.913) this model's rabbit abundance estimates to pellet density in 11 patches and generated a range-wide population estimate of 317, a western clade population of 257, an eastern clade population of 25, and translocated LKMR populations of 35 and 0 on Little Pine and Water keys, respectively. This prediction equation provides managers a quick, efficient, and non-invasive method to estimate LKMR abundance from pellet counts. To quantify the amount of habitat loss and fragmentation that occurred over the last 50 years, I systematically delineated and compared potential LKMR habitat using 1959 and 2006 aerial photographs. Additionally, I investigated if other factors could have reduced the amount of suitable habitat available for the LKMR with a comparison of habitat loss and fragmentation on a developed island and an undeveloped island. Range-wide, I found that number of habitat patches increased by 38, total class area decreased by 49.0%, and mean patch size decreased by 44.3%. Mean shape index increased by 4.2% and mean proximity index decreased by 13%. Both the 1959 and 2006 connectance indices were low while the 2006 set decreased 12.1%. I observed the same patterns of habitat loss and fragmentation on both the developed and undeveloped islands as I did in the range-wide landscape analysis. I found that LKMR habitat has declined in area and become more fragmented over the last 50 years. Habitat loss and fragmentation by development have directly endangered the LKMR; however, sea level rise and woody encroachment also could have historically caused habitat loss and fragmentation. Although development in LKMR habitat was halted, sea-level rise and woody encroachment could continue to alter LKMR habitat.
  • Wildlife biologists and land managers tasked with the recovery of the endangered Lower Keys

    marsh rabbit (LKMR; Sylvilagus palustris hefneri) were in need of a current population estimate as well as

    a method to estimate the LKMR population annually. Habitat loss and fragmentation from population

    growth and development have threatened the existence of the LKMR. Establishing and understanding

    long-term habitat availability for the LKMR is important for determining causes of historical population

    declines as well as designing and implementing successful recovery plans.

    I conducted a range-wide pellet survey and a mark-recapture study to estimate the LKMR

    population. I evaluated the fit of 5 models and considered the variation in behavioral response model the

    best model. I correlated (r2 = 0.913) this model's rabbit abundance estimates to pellet density in 11

    patches and generated a range-wide population estimate of 317, a western clade population of 257, an

    eastern clade population of 25, and translocated LKMR populations of 35 and 0 on Little Pine and Water

    keys, respectively. This prediction equation provides managers a quick, efficient, and non-invasive

    method to estimate LKMR abundance from pellet counts.

    To quantify the amount of habitat loss and fragmentation that occurred over the last 50 years, I

    systematically delineated and compared potential LKMR habitat using 1959 and 2006 aerial photographs.

    Additionally, I investigated if other factors could have reduced the amount of suitable habitat available for

    the LKMR with a comparison of habitat loss and fragmentation on a developed island and an undeveloped

    island. Range-wide, I found that number of habitat patches increased by 38, total class area decreased by

    49.0%, and mean patch size decreased by 44.3%. Mean shape index increased by 4.2% and mean

    proximity index decreased by 13%. Both the 1959 and 2006 connectance indices were low while the 2006

    set decreased 12.1%. I observed the same patterns of habitat loss and fragmentation on both the developed

    and undeveloped islands as I did in the range-wide landscape analysis. I found that LKMR habitat has

    declined in area and become more fragmented over the last 50 years. Habitat loss and fragmentation by

    development have directly endangered the LKMR; however, sea level rise and woody encroachment also could have historically caused habitat loss and fragmentation. Although development in LKMR habitat

    was halted, sea-level rise and woody encroachment could continue to alter LKMR habitat.

publication date

  • December 2009