Tuesday, September 10, 2013

Rodenticides....Unintended Consequences

 If it’s sold on store shelves, it must be safe…right? Not always.

In 2008, the U.S. Environmental Protection Agency (EPA) released new safety measures intended to reduce children’s exposures to rodenticides in the home and reduce risks to wildlife. These measures were to be implemented by 2011 but not all companies complied with the measures.  In response, the EPA recently took action to remove 12 rodenticide products from the market but pending litigation has stopped the ban for now. 

So what’s all the concern since rodenticides kill rodents?  Yes, rodenticides contain active ingredients that kill rodents in varying ways. However, they can also kill or seriously compromise the health of non-target wildlife, children and pets. The Red-tailed Hawk, Great-horned Owl, Bobcat, Mountain Lion, Gray Fox, Red Fox, Black Bear, and Turkey Vulture, to name a few, are species that can be negatively impacted by rodenticides.  In California, the Department of Pesticide Regulation (DPR) has determined that impacts to non-target wildlife by second-generation anticoagulant rodenticides are a statewide issue and is proposing new regulatory action (No. 13-002) to designate those rodenticides as restricted materials and limit the placement of aboveground baits.

So what are rodenticides? Rodenticides are pesticides that contain active ingredients that can be classified into three types: 1) acute toxicants (AT’s), 2) first-generation anticoagulant rodenticides (FGAR’s) and 3) second-generation anticoagulant rodenticides (SGAR’s), and they are placed indoors or outdoors in tablet, pellet and/or paraffin block form. They can even be contained in bait stations. Acute toxicants work in several ways such as impairing nerve cell action or causing cell death.  With anticoagulant rodenticides, the animals’ blood loses its clotting ability and capillaries are damaged, causing the individual to die from internal bleeding. With FGAR’s, animals must consume the rodenticide several times to accumulate a lethal amount of toxin in their body and some animals became resistant to the active ingredient(s).  Therefore, SGAR’s were developed that are more toxic and designed so that lethal concentrations are consumed in just one feeding.  However, it takes several days for the rodent to die during which time it can return to feed on the rodenticide, building up extremely high concentrations in its tissues.  If it becomes prey for predators, those high concentrations of rodenticides are passed to the predator and can be lethal or compromise the non-target animals' health.  

 Aside from direct death due to anticoagulant toxicity, wildlife exposure to anticoagulant rodenticides can weaken an animals' immune system, making it vulnerable to other diseases/infections such as mange, a disease caused by a parasitic mite. Mange causes intense itching, hair loss and eventually thickening of the skin if the host animal is not healthy enough to fight the infestation.  Eventually, the skin may tear leading to bacterial infections and death.  A study conducted in the Santa Monica Mountains (Riley et al 2007) determined that two (2) mountain lions died as a direct result of anticoagulant toxicity, 90% of dead bobcats tested positive for anticoagulants and there was a high level of association in bobcats between severe mange and anticoagulant exposure. In the Puente Hills, one bobcat tested positive for anticoagulants rodenticides, at least one other bobcat died with severe mange while a third with severe mange was captured, treated and re-released. 

Currently, numerous cities and counties are showing support for the EPA and DPR by passing resolutions opposing the sale, purchase and use of certain rat and mouse poison products that pose an unacceptable risk to children, pets and wildlife.  The Board of Directors for the Puente Hills Habitat Preservation Authority passed one such resolution in August 2013 as did the City of Whittier in July 2013.  You can have your voice be heard by submitting comments to the California DPR on their Notice of Proposed Regulatory Action No. 13-002 by October 4, 2013, before 5:00 p.m. More information can be found at: 

Tuesday, April 2, 2013

Stop, look, listen!

If you’ve hiked in the Puente Hills you’ve probably heard drumming on trees or noticed horizontal holes drilled into trees with sap flowing from them; all courtesy of a group of birds called sapsuckers.  Sapsuckers belong to the bird Family Picidae that includes woodpeckers.  There are about 200
species of picids worldwide, of which two species of sapsuckers, Red-breasted sapsucker (Sphyrapicus ruber) and the red-naped sapsucker (Sphyrapicus nuchalis), have been confirmed on Habitat Authority managed land. 

The Red-breasted Sapsucker is a medium sized woodpecker with a red head, nape, throat and breast, cream colored belly, white rump and white moustache stripe.  Preferring to drill sap wells in riparian species, they inhabit forest edges and woodlands.  Breeding occurs from Alaska and British Columbia south to California and wintering grounds are located throughout most of their breeding range. They are cavity nesters and drill out new nest cavities typically annually.  Their diet consists of sap, arthropods and some fruits. 

Red-naped sapsuckers differ in that they have a red head and nape, cream breast and belly.  They breed in the Rocky Mountains and winter in southern California typically along the edges of forests and woodlands, especially groves of aspen and alder.  They are also cavity nesters and their diet consists of sap, arthropods and some fruits. 

Sapsuckers use their strong bills to drill sap holes, collectively called sap wells, into living trees and eat the sap along with some insects that are attracted to, and get trapped by, the sap.  The shape and size of the sap holes differs by species and the holes drilled in these pictures were likely made by the red-breasted sapsucker.  These sap wells can also be an attractant for species like hummingbirds who eat the sap that the sapsucker keeps flowing.  Large sap wells can cause extensive damage to trees leading to tree mortality while other times trees can heal themselves and continue growing.  Not all activities of sapsuckers are problematic.  Sapsuckers usually excavate new nests every year, leaving old nesting cavities for a variety of woodland/forest species to inhabit. 

So when you’re out on the trail, keep your eyes and ears open for these wonderful birds!