A red diamond rattlesnake, Crotalus ruber, from Baja California. Photo by thibaudaronson, used under Creative Commons licence CC BY-SA 4.0.

Urban Vipers 8: Red diamond rattlesnakes (Crotalus ruber) in Loma Linda, California

Posted onJuly 5, 2023byOjibway Massasauga|News and Events, Ojibway Prairie Reptile Recovery, Urban Vipers

The red diamond rattlesnake is a venomous snake that is sometimes at the centre of human-snake conflict, particularly in Loma Linda, California. What research is being done to help the residents of Loma Linda coexist with these beautiful, but potentially dangerous rattlesnakes?

WHAT IS THE RED DIAMOND RATTLESNAKE?

The red diamond rattlesnake (Crotalus ruber) is a moderately large rattlesnake which can grow upwards of 1.2 metres in length, and which typically lives in coastal, rocky shorelines, canyons, and desert slopes. This rattlesnake species has a very restricted global range; it is found only in the southern part of the state of California, USA, and along the Baja California peninsula in northern Mexico.

The red diamond rattlesnake can be easily identified by its reddish colour, distinct white-bordered diamond pattern on its back, and black and white stripes at the end of its tail. This snake primarily eats mammals of varying species and sizes, but has also been known to hunt lizards and birds. It is thought to be preyed upon by roadrunners, kingsnakes, and owls.

In California, red diamond rattlesnakes are threatened by human encroachment and habitat destruction, and they are therefore considered a species of special concern. This designation provides C. ruber with a certain level of legal protection when developers propose new buildings and homes within its habitat. In spite of this protection, rapid development in and adjacent to traditional C. ruber habitats in California has increased the amount of human-snake encounters, particularly in Loma Linda.

Loma Linda University Health Medical Centre in Loma Linda, California. Visible behind are the well known hills that surround the area. Photo credit: Loma Linda University Health.

ARE THERE RED DIAMOND RATTLESNAKES IN LOMA LINDA?

Loma Linda is a small city of roughly 25,000 people, which is right beside an expanse of undeveloped rolling hills and grassland habitat used by red diamond rattlesnakes. These snakes will sometimes travel into bordering residential areas in search of food or shelter; even where 50 to 150m wide ploughed firebreaks have been created between houses and natural habitat, which are essentially unsuitable areas for snakes.

The practice of capturing and moving a “nuisance” animal away from an area of potential conflict with people is called a “mitigation translocation”. Translocation is a better alternative to killing snakes found in residential areas, especially given the conservation concern for this species.

Translocated snakes, however, often experience unnaturally high rates of erratic behaviour and mortality soon after release, which tends to increase with the distance translocated. But, if snakes aren’t translocated far enough, they may return to the site of conflict and continue to pose a risk for snakebite. Does translocation work for the people and snakes of Loma Linda?

Aerial view of the southeast corner of Loma Linda, California. Green circles represent observations of snakes in their natural habitat using radiotelemetry, and red circles represent observations in residential areas. The yellow dashed line outlines a ploughed firebreak (Corbit 2015).

WERE RED DIAMOND RATTLESNAKE TRANSLOCATIONS SUCCESSFUL?

A study was conducted in Loma Linda from 2008 to 2011 to compare the effect of translocation distance on movement and survival of red diamond rattlesnakes (Corbit and Hayes 2022). Thirty adult snakes were translocated: one third were moved a long distance (716 to 6000 m) and two thirds were moved a short distance (less than 716 m). Each snake was implanted with a radio transmitter in order to track its movement during the study.

Snakes subjected to a long-distance translocation (LDT) had an effective home range up to 4.6 times larger than those subjected to a short-distance translocation (SDT), and travelled nearly twice as much per day than SDT snakes. However, one year after translocation there was no significant difference between the two groups of snakes, indicating that it took around one year before LDT snakes established normal home ranges in their new territories.

Relocated individuals demonstrated remarkable homing behavior, often returning to their original capture sites despite being released up to hundreds of metres away. However, LDT snakes were less likely to return to human-dominated areas, and the rate of return to capture sites decreased as the translocation distance increased.

There was no significant difference found in mortality between LDT and SDT snakes in this study, however, this result is not universal for all snake translocations. A similar study conducted in Perth, Australia (see Urban Vipers 6: Dugites in Perth Australia) found that LDT snakes had a mortality rate of 100%, while SDT individuals had a mortality rate of only 50%. Also, snakes living in colder climates develop strong ties to their overwintering sites, and if moved too far, their ability to survive the winter will be compromised. This discrepancy in snake survival highlights the need for species-specific (and possibly even population-specific) research before conducting large-scale mitigation translocations.

HOW CAN LOMA LINDA RESIDENTS COEXIST WITH RED DIAMOND RATTLESNAKES?

With ever-growing development into wild spaces, and with people living so close to snake habitat, humans and rattlesnakes will continue to interact in Loma Linda. The similar mortality rate between translocated snakes and resident snakes paints an optimistic picture for C. ruber in this city.

Mitigation translocations can be a beneficial tool to mitigate snake-human conflict, to reduce both the number of snakes being euthanized and the number of snakebites. By prioritizing habitat conservation and integrating scientific research into management strategies, we can secure a future where humans and these remarkable snakes coexist harmoniously in Southern California’s rocky hills.

“With increased understanding, we too might appreciate venomous snakes as living symbols of wilderness; perhaps we can even afford them a place in modern landscapes” – Harry Greene

REFERENCES

Corbit, A.G. 2015. The dynamics of human and rattlesnake conflict in Southern California. Loma Linda University Electronic Theses, Dissertations & Projects. Paper 347.

Corbit, A.G. and Hayes, W.K. 2022. Human-wildlife conflict at a suburban-wildlands interface: effects of short- and long-distance translocations on red diamond rattlesnake (Crotalus ruber) activity and survival. Diversity. 14: 130.

Dugan, E.A. and Hayes, W.K. 2012. Diet and feeding ecology of the red diamond rattlesnake, Crotalus ruber (Serpentes: Viperidae). Herpetologica. 68 (2): 203-217.

Authorship note: This blog post was a group effort, originally drafted by Remo Boscarino-Gaetano, and edited by Kathleen Woodhouse, Natasha Sawatzky, and Jonathan Choquette.

Urban Vipers 1: The Prairie Rattlesnakes of Lethbridge

Urban Vipers 2: Western Rattlesnakes of Osoyos, BC

Urban Vipers 3: The black mambas of Durban, South Africa

Urban Vipers 4: The jararacas of Sao Paulo, Brazil

Urban Vipers 5: The timber rattlesnakes of Lenexa, Kansas

Urban Vipers 6: Dugites in Perth, Australia

Urban Vipers 7: Javan spitting cobra in Jakarta, Indonesia

WPC appreciates funding support provided by the Ontario Ministry of Environment, Conservation and Parks’ Species at Risk Stewardship Program for WPC’s Ojibway Reptile Recovery Program.