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Daphne Hatch—What Her Study Didn't Tell You


By Dr. Suzanne Valente


Unfortunately, Daphne Hatch in her study of the western snowy plover at Ocean Beach justifies the leashing of dogs based on observations of the number of times dogs chased or inadvertently disturbed the plover.  Click here to view the entire 1996 Daphne Hatch Report.  However, Ms. Hatch conveniently did not document the number of disturbances of the plover or any deaths of plovers perpetrated by predators such as the raven or crow!


The raven and crow are documented predators of the plover, while dogs are not.  Ravens are black, cousins of the crow, and larger-generally about two feet long.  Federal officials, who attribute the soaring numbers of ravens to sharp increases in road-kill and garbage from fast-food restaurants, say the population explosion is troubling, given the bird’s intelligence.


The Daphne Hatch study is an excellent example as to why scientific studies vary in reliability.  Based upon the standards set forth in the medical-dental scientific community (which is my community) her study qualifies as “junk science”.  An operative definition of “junk science” my profession accepts is “a publication that has the tone and trappings of science, but is so fundamentally and demonstrably flawed as to lack any serious claim to credibility”. 


Why do I say this about Daphne Hatch’s study?  First, it is merely an observational study.  This means its conclusions are not based upon specific, quantifiable measurements, they are based upon observations.  Observations alone allow for the participant’s natural biases to influence the results.  For example, a credible scientific study to determine the success of say, a hair growth product, would dictate that the same person would observe the patients at the beginning and end of the treatment to assess the patient’s baseline and subsequent hair growth (or lack of).  This would eliminate the differences inherent in the observations of different people.  The evaluator should have no affiliation with any of the manufacturers of the different products tested, and would not know which patient used which product.  This is necessary to eliminate an evaluator’s desire (even if it is subconscious) to favor a particular product.  The evaluators in the Daphne Hatch study were many different volunteers, so there was no consistency as to the observations.  Some may characterize plover movement as a disturbance; others might believe the plover moved on its own.  The volunteers were all bird enthusiasts, and the specific focus of their study was humans and dogs.  The premise of the study would lead the volunteers to subconsciously expect and want to document disturbance of the plover by dogs and their owners. 


The effects of other wildlife and other possible interferences with the plover’s daily activities were given a brief mention but not factored into the study in any meaningful way.  These issues would be:  beach cleaning, off-road vehicles driven at night, activity of specific predators such as the falcon, non-native vegetation, shoreline erosion control projects (bulldozers), the actual width of the beach available to the plover, weather, helicopters, airplanes, bicycles, vehicles used during the day by Park staff, kites, and an oil spill.  How can you possibly distinguish when a plover flies away to another spot if the cause was the dog 30 feet away, or the plane flying overhead?  In this study, it seems clear the dog would be identified as the factor that disturbed the plover.  The question becomes how does one relate the number of plovers at Ocean Beach from year to year to the activity of dogs and their owners when you have chosen to overlook the effect of all these other variables listed.  It’s preposterous!


Most significant, in my view, is the lack of discussion about ravens or crows and the plover.  Ravens are a known predator of the plover, and have been found in increasing numbers on our California beaches.  Dave Pereksta, a bird specialist for USFWS in Ventura, has said that there have been dramatic increases in the raven population along the coast in recent years. Ravens prey on the eggs of endangered California least terns, western snowy plovers and California condors.  Like seagulls, the ravens are attracted to garbage left behind on the beach, and they often discover the nest of a plover or tern in the process.  “They are so smart that, once they cue in on that … boom, they’ll get every one,…they will literally take every nest out” Pereksta is quoted as saying.


In central California, state parks superintendent Greg Smith has been monitoring the relationship between the crow and the plover at Morro Strand State Beach, among others.   “In the wintertime you’ll see hundreds of crows on that beach.  They’re keying in on the plovers.  They go up to the nest and eat the eggs.  It’s a fairly recent phenomenon.”  Smith noted that only one plover chick survived the last nesting season.  The public (and in some cases just their dogs) have been denied access to sections of the Central Coast beaches as part of efforts to protect the plover.  However, just this summer a docent in Santa Barbara watched a crow pick up and fly away with one of three plover chicks who were being observed in an area closed to the public for the plover’s protection.  It is interesting to note that a study by Kevin Lafferty documenting disturbances of wintering snowy plovers in Santa Barbara acknowledges that the most intense disturbance of plovers is in response to crows.  It is worth questioning whether the science would support the State Parks’ or the GGNRA decision to limit the public and/or dogs access to beach areas in an effort to protect the plover. 


At Ocean Beach, the plover does not nest or breed.  It roosts.  So discussions of their nests or eggs are irrelevant.  To validate her theory, Ms. Hatch chose to focus on the “disturbance” of the plover.   However, it is not established in her study, or any study, that disturbance of the plover results in significant harm to the plover.  It is postulated by Ms. Hatch and others that the energy expended by the plover to avoid the disturbing dog is detrimental to their overall health and ability to breed.  What is the basis for this conclusion?  There is no scientific basis for her assumption.  Consider this:  the plover is known to migrate over 1000 kilometers annually.  In proportion to their size, it is the equivalent of a 6 foot human running 290 marathons.  Does the energy expended when a plover moves 20 or 30 yards to avoid a roaming dog amount to anything significant?  Common sense would indicate that the “disturbance” issue has been way overblown, and no scientific study exists to contradict common sense.  It is just as easy to postulate that the disturbances have a beneficial cardiovascular effect upon the plover!


In fact, this brings up the other problem with the operative hypothesis in this study that dogs off-leash are detrimental to plovers.  The statistics seem to indicate that during the period prior to this study the number of plovers at Ocean Beach was increasing, even though there was no requirement for dogs to be on-leash.  Bias in the design of a study sometimes prevents the scientist from coming to the appropriate conclusion, especially if it happens to be in direct conflict with the operative hypothesis.  For example, we can reflect upon the unfortunate result when GGNRA officials limited access to dogs and their owners at Fort Funston in San Francisco.  The endangered bank swallow population nested in the cliffs adjacent to an area where people and dogs were free to roam.  When access to that area for people and their dogs was prohibited, (because the GGNRA presumed they were disturbing the swallows) the bank swallow population was decimated by birds of prey.  It was interesting to note that the bank swallows subsequently moved their nests to an area of the cliffs where dogs and people were still allowed access.  It has reasonably been concluded by some that the presence of dogs and people has a protective effect upon the bank swallow and the plover with respect to birds of prey like the raven and the crow. 


Because Daphne Hatch’s study at Ocean Beach ignores ravens or crows entirely, we do not have data to determine whether or not the presence of dogs protects the plover from birds of prey.  So, we have a study that does not compensate for participant bias, and is not able to effectively associate cause and effect because too many variables are unaccounted for.  What do we have?  "Junk science".  Daphne Hatch’s conclusions are without merit, and perhaps worse, led to action which may have harmed the plover at Ocean Beach.


From a practical standpoint, it is worth exploring in your beach community if the officials who are banning or restricting dogs are at the same time refusing to deal with the raven or crow population.  Are officials making sure dead wildlife such as sea lions or birds are being promptly removed from the beach and properly disposed of?  Or are the rotting carcasses of these dead creatures left indefinitely on the beach to attract the ravens?  Recently on Ocean Beach we had the carcass of a cow wash up on to the beach where it sat for almost a week before officials removed it.  The dead body was literally covered with ravens, ripping and eating the dead animal’s flesh. 


Litter also attracts the raven and crow.  It might be worthwhile to check with local law enforcement to see if people at the beach are being cited for littering.  Ocean Beach characteristically has massive amounts of litter left on the beach and overflowing the few garbage cans provided.  If Park Rangers are citing for littering, their campaign is decidedly ineffective.  A focused approach to a problem can work.  More garbage cans, whose contents are picked up more frequently would be of great help.  A period of increased ranger presence with admonitions to beachgoers to pick up their trash would be effective.  Several years ago, GGNRA officials decided to address the dog owners who did not pick up after their dogs’ defecation on the beach.  For a period of several weeks, rangers were posted at the main entrances to the beach, and every dog owner was politely asked to show the ranger their dog refuse bag before they proceeded on to the beach.  This campaign worked remarkably well, and it got the point across that dog feces were not to be left on the beach. 


The idea of protecting critical habitat is to protect the ecosystem that has traditionally supported an endangered species, i.e. the plover.  However, the fatal flaw in the science (or lack of) behind the ESA is that by restricting the access of people, dogs and/or horses from critical habitat USFWS officials may be affecting the plover adversely.  Prior to doing such, a full environmental study should be undertaken.  When wolves were systematically eliminated from Yellowstone, it was not expected to have the negative effect that was observed over the years that followed.  Reintroduction of wolves has revitalized the ecosystem in Yellowstone National Park.   With the wolf back, coyote numbers are dwindling, while other animals are rebounding big time.  After a wolf pack has had their fill of a kill of deer or elk, the remains are food for grizzly bears, mountain lions, eagles and ravens.  Grizzlies were seriously threatened before the wolf’s return, and they as well as the plants are recovering.  With elk being eliminated by the wolves, the willow and aspen trees are recovering from the elk’s overgrazing.  The willow and aspen provide food for beavers, who are now building the first beaver dams seen in 50 years.  The succulents that grow in the ponds behind the dams provide additional food for grizzly bears.  Clearly if the situation had been studied thoroughly at the time, the decision to allow the removal of the wolf from the ecosystem would never have been made.


As part of its review in the Federal Register on whether the plover should stay on the ESA threatened species list at all, the agency admits:  “In 30 years of implementing the Act, the Service has found that the designation of statutory critical habitat provides little additional protection to most listed species, while consuming significant amounts of available conservation resources.”  It goes on to say that designating critical habitat “provides little real conservation benefit, is driven by litigation and the courts rather than biology, limits our ability to fully evaluate the science involved, consumes enormous agency resources, and imposes huge social and economic costs.”


I implore Ms. Hatch and the GGNRA to stop their perversion of science to justify their bias against dogs and their owners.   Let’s not repeat the fiasco of the Bank Swallow at Fort Funston when dealing with the plover at Ocean Beach.  Can we get back to the basic fundamentals of science when attempting to solve the problems of both nature and mankind?  Leave the “junk” where it truly belongs, i.e., in the yards designated for its disposal, in the driveways of neighborhood garage sales, and in the mouths of predacious ravens.  Not in what purports to be an objective, scientific study.