Quietly into Oblivion: The Lonely Extinction of the Sacramento Valley Tiger Beetle
California is home to some 40 million people who over the last few hundred years have destroyed tens of thousands of acres of oak woodlands, grasslands, pine forests, thousands of miles of rivers, and other natural habitats converting and developing them into vast sprawling cities and towns, roadways and freeways, agricultural fields, trash dumps, oil and gas fields, dams, and all the other essentials of our society.
This epic gnashing and gnarling clash between Nature and humans has made the Golden State the epicenter for imperiled species extinction in the continental United States. Not only have charismatic animals such as the grizzly bear, jaguar, Santa Cruz kangaroo rat, and Mexican wolf been eliminated from California, but even insects, tiny creatures often not noticed by most people, have vanished as well.
One of these little known insects driven to extinction was the Sacramento Valley tiger beetle. Its only habitat was sandy beaches along the Sacramento and Feather rivers in the Sacramento Valley. Like many species of tiger beetles, its grub-like larvae made vertical pencil-sized holes in the ground. Springing out like a Jack-in-the-box, they grabbed passing ants, flies, and other insects which were taken to the bottom of their burrow and eaten. Like their feline namesake, adult tiger beetles are highly active fast moving predators who use their keen eyesight to chase down and catch invertebrate prey.
Figure 1. Left - Adult Sacramento Valley tiger beetle (length approximately ~1 inch). Top right - tiger beetle larvae in its vertical burrow waiting for passing insect prey . Lower right - burrows of tiger beetle larvae. (photos - https://beetleidentifications.com/six-spotted-beetle/; https://entomology.ces.ncsu.edu/biological-control-information-center/beneficial-predators/tiger-beetle)
Figure 2. Map showing the Sacramento Valley in California
Colonel Thomas L. Casey, an avid amateur entomologist and U.S. Army engineer in the late 19th and early 20th centuries, was the first scientist to recognize the distinctiveness of the Sacramento Valley tiger beetle. In 1913, based on specimens collected at Sacramento, California, Colonel Casey formally named the species in a scientific journal.
The Sacramento Valley tiger beetle was almost certainly always uncommon and never widespread. We know this because tiger beetles, like butterflies, have long been eagerly sought out by both entomologists and amateur collectors who often go to great effort to find them, and unlike many other insect groups, we have a comprehensive knowledge of their taxonomy, biology, and distribution. The animals are so popular there is even a scientific journal, Cicindela, devoted to them which has been regularly published since 1969. Although the Sacramento Valley tiger beetle was uncommon compared to other species, generations of insect collecting entomologists and entomology students at UC Berkeley, UC Davis, and the California Department of Food and Agriculture have ensured the tiger beetles of northern California have been well surveyed.
Between 1913 and 1984, entomologists collected or observed the Sacramento Valley tiger beetle in Sacramento, West Sacramento, Davis, and near the towns of Colusa and Nicolaus. Nearly all of these populations were eliminated by urban development and other human impacts by the 1970s if not earlier. By 1984 , the last living individuals, about 250 adults, were observed on the Feather River near the town of Nicolaus. No specimens collected after that date have been located in the very large and comprehensive tiger beetle collections at the California Academy of Sciences and the Natural History Museum of Los Angeles County.
Urban development and levee construction were gradual and cumulative processes that destroyed the sandy beaches the Sacramento Valley tiger beetle depended on for finding their insect prey, as well as breeding, resting, and other essential behaviours; insecticide drift from adjacent agricultural fields killed them; off-road vehicles and people ran over or stepped on the adults, crushed the delicate larvae in their burrows or destroyed their habitat; and dam, levees, and river channelization annihilated their habitat by artificially altering water levels and flows, either drowning them, especially the early stages or by destroying their habitat with floods.
Intended to reduce the risk of flooding, levees have been constructed along all the rivers and many of the streams in the Sacramento Valley. However, by constricting and straightening the natural floodplains, levees have created what are essentially “fire hoses” whose higher water velocities eliminated sand beaches, native riparian communities, and natural slow moving meanders and oxbows, resulting in the loss of habitat for the tiger beetle as well as salmon, steelhead, sturgeon, birds, and other wildlife.
The construction of Shasta Dam on the Sacramento River in the 1940s almost certainly extirpated Sacramento Valley tiger beetle populations inhabiting downstream sites. But what likely finally pushed the Sacramento Valley tiger beetle to extinction was the construction of Oroville Dam on the Feather River. Built in 1968, it altered the eons old patterns of seasonal water flows. Melting winter snows in the Sierra Nevada and spring rainfall fed rushing high waters in the spring, while the river was reduced to slower shallow flows in the not dry summer and fall. The waters released from the Dam during the dry months resulted in longer periods of higher flows drowning larvae in their burrows and estivating (=hibernating) adults, and changed the soil composition of the beaches required by the Sacramento Valley tiger beetle.
The subterranean early stages of the Sacramento Valley tiger beetle required fine sand with specific humidity levels. If their burrows become too dry or wet, the larvae would attempt to find locations with sand having the proper conditions. The artificially altered river flows resulted in changes in the species’ habitat due to increased amounts of pebbles and rocks instead of fine sands deposited on the beaches, deposition of greater amounts of unsuitable silt, and improved habitat for vegetation on the beaches. The plants eliminated the open areas needed by the adults for thermoregulation, feeding, resting, and mating.
Figure 3. Upper Left - typical sand beach on the Chesapeake Bay, Maryland, inhabited by a tiger beetle closely related to the Sacramento Valley tiger beetle. Note the wide beach consisting of fine loose sand, minimal vegetation, and little human use. Upper Right - Site on the Feather River formerly containing suitable habitat for the Sacramento Valley tiger beetle, but now covered with vegetation which has created adverse environmental conditions for the species. Lower Left - Location on the Feather River near Nicolaus where the last living Sacramento Valley tiger beetles were observed in 1984. The required environmental conditions - open unvegetated fine loose sand are no longer present. Lower Right - Sandy beach on the Feather River now unsuitable for the species due to habitat damage by off-road vehicles and intensive human recreational use.
Figure 4. Upper Left - Types of levees used for flood control in the Sacramento Valley. Their construction requires the removal of native riparian vegetation and suitable habitat for the Sacramento Valley tiger beetle. Lower Left - Rock and boulder riprap is unsuitable habitat for the Sacramento Valley tiger beetle and many other native animals and plants. Some levee districts and the Bureau of Reclamation still regularly remove vegetation growing on dirt levees to prevent the establishment of riparian habitat. Lower Right - Red arrow indicates extensive levee system holding the Feather River in a dramatically channelized and narrowed floodplain just south of the towns of Marysville and Yuba City.
Figure 5. Upper - Rock riprap has essentially turned this portion of the Sacramento River into a “firehose” from a once natural meandering waterway with beaches, and riparian vegetation. Lower - Levees on Feather River with small patches of remnant riparian habitat surrounded by agricultural fields. It lacks fine sand beaches created and maintained by natural seasonal river flows
Historically, as colonies of the Sacramento Valley tiger beetle were lost to natural events, dispersing individuals from other populations would eventually re-colonise the sites. But as increasing human impacts along the once undisturbed rivers of the Sacramento Valley resulted in the increased loss of sandy beach habitats, more and more populations vanished, leaving fewer and fewer tiger beetles to recolonize suitable, but uninhabited locations, until eventually the species was reduced to a single population on the Feather River. When the habitat at that location became unsuitable, the species succumbed to extinction.
Close relatives of the Sacramento Valley tiger beetle found in coastal Southern California, the Midwest, New England, and Long Island in New York are also highly sensitive to the same effects from humans - loss of habitat due to urban development, alteration of river flows, and off-road vehicles and recreational beach use. And these tiger beetles are also precariously holding on to their survival.
The only formal actions taken by the US Fish and Wildlife Service (=USFWS) for the Sacramento Valley tiger beetle under the authority of the Endangered Species Act was to make it candidate for a status review in 1990, and later issue a 90-day finding in response to a May 14, 2003, petition to list the animal under an emergency basis. Extensive USFWS funded survey work from 2001-2004 by Dr Barry Knisely, a tiger beetle expert, found very little remaining suitable habitat and no living animals resulting in the conclusion the species was extinct. The petition to list the Sacramento Valley tiger beetle was denied on October 24, 2008, because extinct species are not eligible for protection under the Endangered Species Act.
It is a tradition in wildlife conservation stories that when lamenting the loss of a species to note it may have held the cure for cancer or other human maladies, or it could have been a keystone species whose extinction will lead to the collapse of an entire ecosystem. For the Sacramento Valley tiger beetle, except to entomologists and naturalists who value its distinct identity, it’s unlikely it had any special or unusual values to Man.
So why should anyone care the Sacramento Valley tiger beetle is extinct?
The now retired USFWS special agent who trained me, and was himself originally educated as a Jesuit, explained the very simple reasons why we should care about the Sacramento Valley tiger beetle, and the other plants and animals who are our fellow travelers on Planet Earth. First, a Nation is defined is defined by its laws, and the Endangered Species Act says that we, the American People, value Life; and second, a living species, even a tiny insect, has value far beyond any dollar value or material worth we humans may choose to give it. And that’s why we fight to save imperiled plants and animals and mourn their loss - simply because they exist.
And so it was, on an unknown day sometime in the 1980s, the last Sacramento Valley tiger beetle quietly died and with its passing, the species vanished forever from the Earth. Only entomologists and perhaps a few others knew of its existence when there were still living animals, and certainly no human was present to witness its extinction. For this is the way the World is ending, not with a bang, but a whimper.
References
Brust, M.L., W.W. Hoback, K.F. Skinner, and C.B. Knisely. 2006. Movement of Cicindela hirticollis larvae in response to moisture and flooding.
Casey, T.L. 1913. Memoirs on the Coleoptera IV. I - Studies in the Cicindelidae and Carabidae of America. 1-192. New Era Printing Company, Lancaster, Pennsylvania
Duran, D.P., C.N. Dickey, and C.B. Knisely. 2004. An mDNA analysis of the Sacramento Valley tiger beetle, Cicindela hirticollis abrupta. Final report. Vanderbilt University, Nashville, Tennessee
Fenster, M.S. and C. B. Knisely. 2006. Impact of dams on point bar habitat: a case for the extirpation of the Sacramento Valley tiger beetle, C. hirticollis abrupta. River Research and Applications 22(8): 881-904
Fenster, M.S. 2004. Part II. Geologic and hydrologic assessment of the Cicindela hirticollis abrupta habitat in the Sacramento River valley, California. Final report. Randolph Macon College, Ashland, Virginia
Graves, R. C., M.E. Kerici, and A.C.F. Graves. 1988. Geographic variation in the North American tiger beetle, Cicindela hirticollis Say, with a description of five new subspecies (Coleoptera: Cicindelidae). Canadian Entomologist 120: 647-678.
Knisely, C.B. 2004. Biology and conservation of the Sacramento Valley tiger beetle, Cicindela hirticollis abrupta. Final Report. Randolph Macon College, Ashland, Virginia.
Knisely, C.B. And M.S. Fenster. 2009. Apparent extinction of the tiger beetle, Cicindela hirticollis abrupta (Coleoptera: Carabidae: Cicindelinae). Coleopterist Bulletin 59(4): 451-456
Kritsky, G., N.T. Gallagher, J. Smith, and A. Watkins. 1999. The decline of Cicindela hirticollis Say in Ohio (Coleoptera: Cicindelidae). Ohio Biological Survey Notes 2: 49-51
Leonard, J.G. and R.T. Bell. 1999. Northeastern tiger beetles. A field guide to tiger beetles of New England and eastern Canada. CRC Press, nNew York, New York.
Mawdsley, J.R., M.D. Schlesinger, T. Simmons, and O.J. Blanchard. 2013. Status of the tiger beetle Cicindela hirticollis Say (Coleoptera: Cicindelidae) in New York City and on Long Island, New York, USA. Insecta Mundi 0317: 1-7.
Nagano, C.D. 1980(82). Population status of the tiger beetles of the genus Cicindela (Coleoptera: Cicindelidae) inhabiting the marine shoreline of Southern California. Atala 8(2): 33-42
Pearson, D.L., C.B. Knisely, D.P. Duran, and C. J. Kazilek. 2015. A field guide to the tiger beetles of the United States and Canada. Oxford University Press, Oxford, U.K.
Scott, R.G., K.Y. Buer, D. Forwalter, J. Faggard, J. Bettes II, and R. Hall. 1994. Sacramento River bank erosion investigation. California Department of Water Resources, Sacramento, California
U.S. Fish and Wildlife Service. 2008. Endangered and threaten wildlife and plants; 90-day finding on a petition to list the Sacramento Valley tiger beetles as endangered. Federal Register 73(207): 63421-63424