During the Covid-19 pandemic, many countries implemented social distancing measures, which significantly reduced transmission rates of the virus. Scientists at Royal Netherlands Institute for Sea Research (NIOZ), Wageningen University & Research (WUR) and Swiss Federal Institute of Technology Lausanne (EPFL) have now found that grey seals and harbour seals in the Dutch Wadden Sea display different social distancing.
This may be an evolutionary consequence of varying disease susceptibility .. Furthermore, the observed differences between grey and harbour seals can be used to differentiate species in aerial surveys.
A cross-disciplinary team of researchers has come up with a new approach to study fine scale distribution patterns of hauled out seals. In their study, published in Royal Society Open Science, they use aerial images to compare between the distribution patterns formed by harbour and grey seal colonies. "By measuring the distance of every seal to its neighbours, we found that harbour seals stay at larger distances from conspecifics than grey seals do", according to Anne Grundlehner, marine ecologist at Wageningen Marine Research.
Spreading diseases
This finding is particularly interesting in the context of pathogen transmission. "Harbour seals appear to be less resistant to respiratory viruses than grey seals. Seals in the Wadden Sea for instance, suffered from two outbreaks of the Phocine Distemper Virus (PDV) in 1988 and 2002", Grundlehner continues. "During these outbreaks, harbour seal populations were reduced by up to 50%, whereas grey seals remained relatively unharmed by the same virus. It is possible that the larger distances we see in harbour seals reflect an evolutionary response to the species' pathogen susceptibility."
Harbour seals appear to be less resistant to respiratory viruses than grey seals.
