Monthly Archives: April 2012

Declines in Irish raptor populations due to rodenticides

Irish raptors have shown dramatic decline over the past half century, of which agricultural pesticides may be a major cause.

Placement of poisoned ‘meat baits’ on farms, as a means of killing foxes, is legal in Ireland, though poses a threat to many raptor species. The widespread use of poisons in rodenticides may be consumed in large quantities by species such as Barn owls, which have declined by over 50% in the past 25 years. A recent analysis of a Golden eagle corpse, which have recently been reintroduced to Ireland, showed toxin poisoning to be the cause of death. It is believed the bird fed on a nearby lamb carcass, laced with the toxin Nitroxynil.

Barn Owl (Tyto alba), Luc Viatour

Toxins threaten raptors in two ways: through direct consumption of unprotected meat baits, and through biomagnification, as pesticides accumulate over time in the body from eating numerous infected prey. Pressures such as habitat destruction and severe winters have further exasperated these problems.

Similar problems have caused drastic decline in species such as the Californian Condor, Brown Pelican, Bald Eagle and Peregrine Falcon. DDT (Dichlorodiphenyltrichoroethane) was a heavily used insecticide in the early nineteen hundreds, since banned in many countries due to it’s devastating effects on wildlife. Egg-shell thinning resulted in reduced reproductive success, and populations of several raptor species plummeted. The Californian Condor surviving only through a captive breeding programme, and pesticide use has since been increasingly regulated.

Though toxins such as those used in rodenticides are highly lucrative within the agricultural business, their effects must be intensely researched if we are to prevent harm to wildlife. To date, the Californian Condor project has costed over $35million, and whilst populations are increasing, they are still low. Barn Owls, Kestrels and Long-eared Owls are all noted as being particularly vulnerable to rodenticides, whilst ‘meat bait’ and general pesticide use further threatens raptor populations in Ireland. At present BirdWatch Ireland is at the centre of such issues, monitoring to identify further population decline, with continued conservation programmes helping many declining species.


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Speedboats and The Florida Manatee: Conserving Trichechus manatus latirostris

The Florida manatee is a large, herbivorous marine mammal found in warm fresh and saltwater along the Florida coastline. Recent recovery of this endangered subspecies has resulted in conflict between conservation experts and boaters of the region, complicating its conservation.

Propellers and boat hulls can cause serious damage to manatees, and resulted in 88 deaths in 2011 alone, as well as many serious injuries. Boating, climate change and waterway alterations caused significant population decline. Its confinement to warm waters puts it at further risk as populations are small, with limited unaffected habitat to move into. Coastal development and waterway alterations further reduce area suited to manatees, whilst climate change threatens to alter those which prevail. After conservation effort, the current population is estimated to be around 3000 individuals, and are listed as endangered.

Trichechus manatus latirostris, Unknown

At present, Florida manatees are protected by several laws, such as the Endangered Species Act and Florida Manatee Sanctuary Act. Speed limits have been introduced, public awareness raised, and injured manatees rehabilitated.

The US Fish and Wildlife Service, which monitor the subspecies, have recently reported stable to increasing populations, good adult survival and promising reproductive rates. Action to downlist the Florida manatee, from ‘endangered’ to ‘threatened’, has since been proposed, whilst pressure from boaters pushes officials to relax strict speed and zone policies. But despite this, conservation experts stress that the Florida manatee is still threatened. If protection is too lax, populations will fall, whilst possible future threats, such as changing waterways and climate change, make the needs of the Florida manatee hard to quantify. Conflict between conservation scientists and boaters continues, though such attention may benefit the Florida manatee, whose state consequently continues to be closely monitored by scientists and the public alike.

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