Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Graduate School



First Advisor

Jake Ferguson


This study measured the concentration of the stable isotopes Carbon and Nitrogen within the tissues of free-roaming and indoor cats on the Hawai’ian islands. This study aimed to determine whether cats are consuming more human provisioned or wild food sources and whether their diet is having a negative impact on endemic species; with a focus on assessing impacts on conserved bird populations. We hypothesized that human provisioned food sources have higher levels of carbon due to the amount of corn fillers within them, while wild food sources are more Nitrogen rich. We found that indoor and feral cats sampled from Urbanized areas do have higher levels of Carbon within their tissues, indicating that they are consuming the food that is being provided for them by humans. Nitrogen levels are higher in organisms that consume large amounts of protein and as expected, the cats that were sampled in protected natural areas with less human traffic, had higher Nitrogen signatures than Carbon. When comparing the Nitrogen signatures of the domesticated free roaming cats and the feral free roaming cats, there was not a significant difference found between the Nitrogen signatures of each population. This suggests that domesticated cats with outdoor access continue to partake in predatory behavior contributing to the decline of island fauna. Our results are consistent with past work that has shown that free roaming cats continue to have a substantial impact on wildlife in the Hawaiian Islands While the effects of cats in managed wild lands have been mitigated by improvements in policy and practice over the last several decades. Even small numbers of cats in these protected areas can produce considerable damage to native biota.

Digital Object Identifier (DOI)