Burning issues in conservation biology: The effect of reproductive season prescribed fire on an endangered insect species, Nicrophorus americanus (Coleoptera: Silphidae)

Tallgrass prairie ecosystems evolved intimately with disturbance.  Fire has historically altered biotic and abiotic grassland dynamics, and is known to alter the landscape in ways that influences herbivore foraging patterns.  While fire has been historically suppressed in grasslands, managers have increasingly turned to prescribed burning to replicate natural and aboriginal fire frequencies associated with healthy tallgrass habitats.  Insects are vital components, and numerous factors within this ecosystem are known to influence insect diversity and abundance which can be affected by both a change in above-ground foliage dynamics and foliage spatial distribution.  Insects respond to fire in a variety of ways and can be characterized as fire-tolerant, intolerant, or neutral, with a few groups identified as being fire-dependent.  Some researchers stress caution in the use of fire in grassland habitats due to the inhibition of population growth or direct mortality of certain threatened or endangered insects.  The unique reproductive behaviors of the Nicrophorus genus have been the focus of intense research, but experimental investigations elucidating decline hypotheses related to disturbance are absent from the literature.  With regard to disturbance by fire, preliminary data from historic prescribed burn records combined with field studies at an Oklahoma field site show a benefit of fire to American burying beetle abundance over the long term, but prior to this study, nothing was known regarding how fire dynamics such as seasonality may affect abundances.  We report here that American burying beetle abundance was reduced by 90% following reproductive season prescribed fire, and have increased to 50% of pre-burn abundances in the three years following the experiment.  Consequences for conservation will be discussed.