1. A GPS/GIS Evaluation of Human Encroachment of Nesting Sites and the Habitat of Olive Ridley Sea Turtles
(Lepidochelysolivacea) on the Urbanizing Beaches of Nuevo Vallarta, Nayarit, Mexico
Julia Carrillo
Capstone Advisors : Dr. Yong Lao & Dr. Manuel Carlos
Spring 2012
Introduction Methods
The beaches of Nuevo Vallarta, Nayarit, which include Flamingos, Bucerias and Mayan Palace beaches, are Nest Data
located on Mexico's Pacific coast. These beaches have nesting populations of Olive Ridley sea turtles that A table was provided by NVSTP and its sponsors. Information collected on this table is sent to overseeing government
exceed all others in the state, the Central Coast and the Northwest of Mexico (M. Carlos pers. com). Nuevo agencies. Each nest included data such as date, time, relative location, moon phase, observed tide phase, egg count, and
Vallarta has fourteen kilometers, about eight and a half miles of beachfront property, seven miles of vertical zone of deposition. The 14km beach was divided into 0.5km sections. The distribution of nests and egg count
shippable water channels, and a 300 slip marina. It is located 20 minutes north of Puerto Vallarta in the along the beach were evaluated using descriptive statistics.
adjacent state of Jalisco. The area has been designated for tourist resort development and recently was made
part of the Riviera Nayarit. It is also the site of a sea turtle conservation effort that is being carried out by Ethnography
the Comisión Nacional de Áreas Naturales Protegidas (CONANP) and the Mexican non-governmental In order to evaluate nesting data outliers I needed to visit the site. Through participant observation I was able to
organization, AMA MEXICO A.C. through the Nuevo Vallarta Sea Turtle Preserve (NVSTP). Rapid resort understand some of the challenges facing conservation efforts. Additionally, use of this technique provided evidence
development and urbanization of beaches leads to disturbance and habitat fragmentation which reduces unavailable through quantitative methods.
biodiversity and leads populations to extinctions (Davenport & Davenport, 2005) Although, sea turtles face
many challenges for survival, both researchers and conservationists agree that the largest anthropogenic GPS
threat to sea turtles is coastal development. (Donlan, Wingfield, Crowder, & Wilcox, 2008) The purpose of GPS was chosen as the method to measure human intrusion on nesting habitat. A Trimble GeoXM GPS device was
this study is to measure and document human intrusion on sea turtle nesting habitat on a recently urbanized used to measure human development on beach shores. This included all beach front structures such as recreational
and commercialized beach. This study also describes nesting preferences along the beach. sporting courts, palapas (shaded structures made from palm trees ), and areas used to store aquatic recreational vehicles.
Most of the 14km of protected beach was measured, small pockets were not mapped due to fast currents emptying from
rivers due to mass rains. GPS was also used to map areas of human drainage and photographs were used to document
Research Questions current pollution to monitor changes. In order to asses compliance of federal laws on coastal habitat high tide needed to
be measured with GPS. To measure loss of protected habitat, available beachfront area needed to be quantified.
(1) Can we characterize the nesting distribution along the North Shore of the Bay of Banderas?
(2) Can we quantify and document human drainage to the sea?
(3) How much protected habitat have humans removed from available nesting use?
Analysis
All GPS data collected was exported from the device using Trimble GPS Pathfinder Office 9.2. The data was
differentially corrected using a base station 70km away in Colima, Mexico. After export, data was imported into
ArcMap 10.0. To quantify human intrusion, a 20 meter buffer of high tide was used as the total available area.
Measured urbanization within the buffer was removed from available nesting grounds. Data collected on drainage
was displayed and had photographs linked to each point.
Figure 1.Average egg distribution for July 2011 vs. protected beach zone. The distribution of egg
count varied little. This showed little variation among 0.5km sections.
Total Protected area (m²) 157973
Human development (m²) 43705
Available nesting grounds (m²) 114268
Habitat loss 27.67%
Figure 6.Coastal habitat available for nesting and
human development within this area measured
with GPS.
Figure 2. Nesting incidences throughout 14km of protected beaches. Comparison of beach
segments clearly shows nesting preferences with areas of higher concentration.
Figure 4. Beach contamination sites less than 0.25 miles from the turtle Figure 5. Contamination less than 0.25 miles south of NVSTP.
preserve are shown in green triangles. Area in purple is protected habitat lost to Locations accompanied by photographs.
human development.
Results
Nesting data showed that sea turtle nesting varied along the 14km coast. Turtle nesting throughout the beach was
disproportionate with a hotspot at the 11.5-11.9 km range (Fig. 1). Average egg count along the beach was shown to
remain constant with only small differences found along the shore (Fig. 2). Additionally, a dot density map shows the
distribution along the beach, highlighting areas with high nesting incidences. (Fig. 3). All visible human drainage that
emptied to the ocean was mapped and had photographs taken to monitor changes. Throughout the study area 26 ocean
draining locations were found. Maps of local water contamination 200 meters north of the NVSTP (Fig. 4) & and south of
the NVSTP (Fig. 5). Total federally protected habitat from high tide extending 20 meters inland was measured to be
157,973 m². Human development was measured to occupy 43,705 m². Allowing only for 114,268 m² available for sea
turtle nesting. Urbanization has lead to a 27.67% loss in protected coastal habitat on these shores (Fig. 6).
Discussion
Although average nest size along the beach was similar, distribution of nests varied with as few as 1 nest and other 0.5km
sections with over 100 nests in that month. Areas with ocean draining and accompanying photographs will be used to
monitor changes or note additions. Since sea turtles return to the same beaches where they hatched to later nest, it would
be essential to maintain or strengthen conservation efforts in highly nested areas. Additionally, Olive Ridley's are only one
of two sea turtle species that partakes in arribada nesting behavior and unlike solitary nesting, arribadas are mass
aggregations with hundreds to thousands of turtles all laying their eggs in small beach areas within a few nights (Plotkin,
Rostal, &Byles, 1997). A characterization of their nesting preferences along the protected shore would help current
conservation efforts by guiding biologists to highly nested locations so that they may increase poaching protection if
needed. Moreover, these hotspot areas are important to consider for further beach development and for the placement of
beach lighting due to the negative effects it has on adult and especially hatchling navigation.
Literature Cited
±
Davenport, J., & Davenport, J. L. (2005). The impact of tourism and personal leisure transport on coastal environments: A
Review. Estuarine Coastal and Shelf Science. 67 : 292-280.
Donlan, C., Wingfield, D., Crowder, L., et all. (2010). Using expert opinion surveys to rank threats to endangered species:
A case study with sea turtles.
Conservation Biology. 24 (6): 186-195.
0 0.5 1 2 3 4
Kilometers
ESRI 2011. Environmental Systems Research Institute. ArcGIS (Version 10.0). Redlands, CA. http://www.esri.com.
Figure 3. Dot density map with nesting incidences for July 2011, each color represents a different range in count per each 0.5km section. Plotkin, P.T., Rostal, D.C., Byles, R.A. et al. (1997) Reproductive and developmental synchrony in female
Lepidochelysolivacea. Journal of Herpetology. 31(1):17-22.
Trimble 2002. Trimble Navigation Limited. GPS Pathfinder Office (Version 9.2). Sunnyvale, CA. http://www.trimble.com.