**Population Status**

The Tucson Shovel-nosed snake has declined rapidly since the mid 1970s
(Rosen 2003).

Rosen (2003) defines four historic and current populations of the Tucson
Shovel-nosed snake:

> "As currently mapped, this taxon was known from the margin of the
> Arizona Upland in places where it has been severely impacted by
> suburban sprawl: Scottsdale region (probably extirpated by urban
> sprawl and agriculture), Florence region (uncommon, facing continued
> sprawl), Casa Grande region (severely impacted by agricultural
> development), and Avra Valley (also affected by agriculture and now,
> potentially, urban sprawl)."

Unfortunately, Rosen's very general descriptions represent the best
available information we are aware of. The 2004 petition notes one
exception to this, which is surveys that Rosen et al. conducted in Avra
Valley,

> "After an extensive survey, Rosen (2003) and his associates failed to
> locate the species. The survey was conducted in areas where Tucson
> Shovelnosed snakes had historically been observed up to 2-3 times per
> night through the mid-1970s, suggesting the snake has sharply and
> severely declined. Rosen (2003) cautions that although it has declined
> severely, the Tucson Shovel-nosed snake may not be extirpated in Avra
> Valley."

Rosen (2004) also reported the occurrence of a Tucson Shovel-nosed snake
near Picacho, north of the Avra Valley, demonstrating that the species
is not yet regionally extirpated.

It is obvious from the dearth of information that additional field
research is needed to fully understand the status of the Tucson
shovel-nosed snake's population. However, it is clear that this species
has vanished from extensive areas where it was once extant, and that
without status as a threatened or endangered species, there will not be
requisite regulatory mechanisms, funding, research and recovery efforts
needed to reverse this alarming trend.

**THREATS**

**Habitat Destruction and Modification**

Because habitat for the Tucson shovel-nosed snake coincides with valley
bottoms and flats, it is not surprising that both habitat quantity and
quality for this species have been compromised. These same flat,
accessible areas are the same areas where agriculture, urbanization and
off-road vehicle use have and continue to be concentrated. The majority
of these lands tend to be in State Trust and private lands, where
development and concomitant habitat destruction is occurring at a rapid
pace. For instance, potentially suitable habitat for this species is
being developed at an alarming rate in Pinal County and within the
jurisdictional boundaries of the Town of Marana, which collectively
represent the fastest growing centers of human population in Arizona.

**Off-Road Vehicle Use**

With off-road vehicle (ORV) use becoming more popular and pervasive, it
should be recognized as a growing threat to the Tucson shovel-nosed
snake. ORV use degrades snake habitat (Luckenbach and Bury 1983), can
cause direct mortality (Himes et al. 2002), and can decrease
reproductive success (Burger et al. 2007).

Rosen (2008) highlights a specific area where ORV use threatens the
snake:

> "The Tucson Shovel-nosed Snake may also persist on State Lands between
> the Pima County line and Red Rock, near Pinal Air Park. These lands
> are under long-term lease to the University of Arizona, which might
> facilitate conservation there. Off-road vehicle recreation is so
> intensive in this area that major ecological damage is occurring. The
> activity seems completely un-regulated, and the damage has rapidly
> become more widespread and intensive during just the past few years".

The Arizona Game and Fish Department's Tucson Shovel-nosed Snake
abstract (2002) notes off-road vehicles as a threat to this species,
stating plainly: "Off-road vehicle activities **will adversely affect**
this species". \[emphasis added\]. Something that will adversely affect
a species is clearly a threat that should not only be recognized, but
quantified and considered within the context of a listing decision.

**Climate Change**

Climate change is now widely recognized as one of the leading threats to
biological diversity globally. Climate is a key driver of vegetation
composition and net primary productivity. This in turn directly impacts
ecosystem structure and function, and will likely have impacts upon the
entire food chain. University of Arizona (U of A) climate models
document current, and predict future, above average warming trends in
the Sonoran desert ecoregion which may exacerbate the extremes of
previous precipitation patterns.

Seager *et al*. 2007 examined future subtropical drying by analyzing the
time history of precipitation in 19 climate models. Of the total of 49
individual projections conducted with the 19 models, only 3 projections
show a shift to a wetter climate. In the multimodel ensemble mean, there
is a transition to a sustained drier climate that begins in the late
20th and early 21st centuries in the southwestern United States and
parts of northern Mexico. In general, large regions of the relatively
dry subtropics dry further, whereas wetter, higher-latitude regions
become wetter still. This pattern of subtropical drying and moistening
at higher latitudes is a robust feature of current projections with
different models of future climate. Seager (2007) explains the drying of
subtropical land areas that, according to the models, is imminent or
already under way is unlike any climate state we have seen in the
instrumental record. It is also distinct from the multidecadal
megadroughts that afflicted the American Southwest during Medieval
times. The most severe future droughts will still occur during
persistent La Niña events, but they will be worse than any since the
Medieval period, because the La Niña conditions will be perturbing a
base state that is drier than any state experienced recently (Seager *et
al*. 2007, [Science]{.underline}, 25 May 2007, Vol. 316, pp. 1181-1184).

While the exact impacts of climate change upon the Tucson shovel-nosed
snake and it's habitat is unclear at this time due to a lack of research
and uncertainty of future climate change impacts, it is clear that based
upon the projections of current climate change models, anticipated
changes in temperature and precipitation may have dramatic impacts upon
the desert Southwest and its ecosystems, and should be considered within
the context of an ongoing and foreseeable threat to the Tucson
shovel-nosed snake. The DPS proposed represents the easternmost portion
of the species' range. Hape and Petit (2005) argue that populations
occurring at the margins of a species' range frequently harbor unique
genotypic and phenotypic characteristics crucial to the species'
response to **changing environmental conditions and future
persistence**.

**\
Taxonomic Status**

Recent research conducted by Wood et al. (2007) did not find genetic or
morphological support for the currently accepted division of *Chionactis
occipitalis* into four subspecies. However, the authors encouraged a
cautious interpretation of the results. The morphological analysis
sample size was comprised of only 32 data points (based on population
means), but included only **three** data points for *C.o. klauberi*.
Given that *C.o. klauberi* is represented by such a small number of data
points, the results are accordingly restricted. In addition, key
taxonomic features such as color and interspace maculations were not
included in the analysis because these characters are bleached by the
preservative used (Wood et al. 2007). Such morphologic features are
important characteristics that have defined the subspecies in the past
(Klauber 1951, Mahrdt et al. 2001, Crother 2008).

As noted in the 90-day finding, the Wood et al. (2007) genetic analysis
was limited to only mitochondrial DNA. Therefore, the results from this
genetic research should not be interpreted as complete or entirely
conclusive. Wood et al. (2007) state, "We would encourage further
hypothesis testing using increased genetic sample sizes and nuclear DNA
data to help resolve these (classification) alternatives." As noted
above, we submit that additional genetic research (namely nuclear and/or
microsatellite genetic testing) is needed to better inform the taxonomic
standing of the Tucson shovel-nosed snake. However, in lieu of such
additional research, there is sufficient data to suggest that this
subspecies qualifies as threatened or endangered now, if only via a
newly created distinct population segment. In the case that FWS should
reverse its determination that *C.o. klauberi* is a valid subspecies, as
stated in the 90-day finding, we request listing for a Northeastern
Sonoran Desert Distinct Population Segment of *C. occipitalis*
consisting of *C. o. klauberi* and its intergrade with *C. o. annulata,*
as called for by the Center for Biological Diversity.

**Critical Habitat**

Since the 2004 petition, new data and information have become available
regarding habitat requirements of the Tucson Shovel-nosed snake. Rosen
(2008) notes that all four 21st-century records of the Tucson
Shovel-nosed Snake are from level, valley bottom or mid-valley habitats
rather than bajadas or even lower bajadas. Rosen also reports that
historically, shovel-nosed snakes may have been primarily associated
with sandy rises, small drifts, low stabilized mini-dunes, and similar
formations created by wind and shifting valley floor arroyo channel
braids. These habitat features have largely been elminated or degraded
by agriculture and other human activities. Thus, it is important that
all remaining areas of intact valley floor flats with suitable sand
substratum be designated as critical habitat for this species, as well
as connective habitat between such areas. Rosen (2008) proposes that a
potential explanation for the disappearance of this species from intact
habitats may be related to an undocumented metapopulation collapse.
Conserving and/or restoring dispersal corridors in connective habitats
will be necessary to maintain natural genetic interchange between
subpopulations. Rosen (2008) states, "We currently have no basis for
assuming that setting aside remaining small habitat areas will allow us
to successfully manage and conserve declining species in the study
region". Thus, designated critical habitat should not only include
remaining high-quality shovel-nosed snake habitat, but dispersal
corridors as well so as to create a network of habitat that can sustain
healthy metapopulation dynamics.

**Regulatory Mechanisms**

Currently, there is no federal or state status identified for the Tucson
shovel-nosed snake. Therefore, regulatory mechanisms that might achieve
conservation or recovery are clearly inadequate, and the continued
decline of this species is evidence of this fact. The Tucson
shovel-nosed snake is a "Priority Vulnerable Species" that is being
considered and analyzed as a potentially covered species under Pima
County's multi-species habitat conservation plan (HCP). However, this
habitat conservation plan has not yet been officially adopted.
Similarly, this species will be covered under the Town of Marana's and
the City of Tucson's Habitat Conservation Plans (Greater Southlands and
Avra Valley HCPs), but these plans are also still under development and
have not yet been adopted. Pinal County, where the majority of potential
habitat for this species exists, does not have and is not currently
developing a habitat conservation plan. Thus, even if this species is
covered under HCPs that are anticipated to be adopted, there are still
inadequate regulatory mechanisms to protect this species from
extinction.

**Works Cited**

AGFD Arizona Game and Fish Department. 2002. *Chionactis occipitalis
klauberi*. Unpublished abstract compiled and edited by the Heritage Data
Management System, Arizona Game and Fish Department, Phoenix, AZ. 4 pp.

Burger, J., R.T. Zappalorti, M. Gochfeld, and E. DeVito. 2007. Effects
of off-road vehicles on reproductive success of pine snakes (*Pituophus
melanoleucus*) in the New Jersey pinelands. Urban Ecosystems
10(3):275-284.

Crother, B. I. (ed.) 2008.  Scientific and Standard English Names of
Amphibians and Reptiles of North America North of Mexico, with Comments
Regarding Confidence in Our Understanding.  SSAR Herpetological Circular
29. iii + 82 pp.

Hampe, A. and R.J. Petit. 2005. Conserving biodiversity under climate
change: the rear edge matters. Ecology Letters 8:461--467.

Himes, J.G., L.M. Hardy, D.C. Rudolph, and S.J. Burgdorf. 2002. Growth
rates and mortality of the Louisiana Pine Snake (*Pituophis ruthveni*).
Journal of Herpetology 36(4):683-687.

Klauber, L.M. 1951. The Shovel-Nosed snake, *Chionactis* with
descriptions of two new subspecies. Transactions of the San Diego
Society of Natural History, 9(9): 141-204.

Luckenbach, R.A. and R.B. Bury. 1983. Effects of OHVs on the Biota of
Algodones Dunes, Imperial County, California. Journal of Applied Ecology
20:265-286.

Mahrdt, C.R., K.R. Beaman, P.C. Rosen, and P.A. Holm. 2001. *Chionactis
occipitalis*. Catalogue of American Amphibians and Reptiles 731:1-12.

Rosen, P.C. 2003. Avra Valley snakes: Marana survey report for Tucson
Shovel-Nosed Snake (*Chionactis occipitalis klauberi*). Final Report on
Shovel-Nosed snake prepared for Town of Marana. University of Arizona,
Tucson, AZ.

Rosen, P.C. 2008. 2007 survey results for the Tucson Shovel-Nosed Snake
(*Chionactis occipitalis klauberi*), with evidence for ecological change
in south-central Arizona. Final Report. 1 January 2008

SDCP. 2004. Sonoran Desert Conservation Plan: Draft Pima County
Multi-Species Conservation Plan. Prepared for Pima County by RECON
Environmental, San Diego, CA.

Seager, R., M. Ting, I. Held, Y. Kushnir, J. Lu, G. Vecchi, H. Huang, N.
Harnik, A. Leetmaa, N. Lau, C. Li, J. Velez, and N. Naik. 2007. Model
Projections of an Imminent Transition to a More Arid Climate in
Southwestern North America. Science 316(5828):1181-1184.

U.S. Department of the Interior Fish and Wildlife Service. 2008.
Endangered and Threatened Wildlife and Plants; 90-Day Finding on a
Petition To List the Tucson Shovel-Nosed Snake (*Chionactis occipitalis
klauberi*) as Threatened or Endangered with Critical Habitat.

Wood, D.A., J.M. Meik, A.T. Holycross, R.N. Fisher, and A.G. Vandergast.
2007. Molecular and phenotypic diversity in *Chionactis occipitalis*
(Western Shovel-nosed Snake), with emphasis on the status of *C.o.*
*klauberi* (Tucson Shovel-nosed Snake). Conservation Genetics. 1566-0621
(Print) 1572-9737 (Online).