Dramatic improvements in beach water quality following gull removal

Area of Science:

• Environmental Science
• Microbiology
• Wildlife Management

Background:

• Gulls are recognized as a significant source of fecal contamination in surface waters.
• Recreational beaches have explored gull control strategies to enhance microbial water quality.

Purpose of the Study:

• To assess the effectiveness of using trained dogs to deter gulls from a Lake Michigan beach.
• To quantify improvements in microbial water quality following gull control measures.

Main Methods:

• Gulls were harassed using trained dogs to reduce their population on the beach.
• Fecal indicator bacteria (Enterococcus spp., Escherichia coli) and potentially pathogenic bacteria were measured.
• Measurements utilized both culture methods and quantitative polymerase chain reaction (qPCR) before and during gull control.

Main Results:

• Average daily gull populations decreased from 665 to 17 during dog intervention.
• Significant reductions in Enterococcus spp. and Escherichia coli densities were observed (p < 0.001 and p = 0.012/p = 0.034).
• Potentially human pathogenic bacteria, present on 64% of days prior, were absent during gull intervention (p = 0.005).

Conclusions:

• Harassment by trained dogs is an effective method for gull population control on beaches.
• Gull removal significantly improves microbial water quality by reducing fecal indicator bacteria and pathogens.
• This study demonstrates gull removal as a successful remedial action for enhancing beach water safety.