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Wheat fields as an ecological trap for reptiles in a semiarid
Guy Rotem
, Yaron Ziv
, Itamar Giladi
, Amos Bouskila
Spatial Ecology Lab, Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Israel
Behavioral Ecology Lab, Ben-Gurion University of the Negev, Beer-Sheva, Israel
article info
Article history:
Received 27 January 2013
Received in revised form 8 August 2013
Accepted 18 August 2013
Ecological trap
Habitat selection
Trachylepis vittata
Intensive agricultural activity over large areas on earth, which is necessary to meet the increasing
demand of a growing human population, may lead to biodiversity loss. This loss may be mitigated by
keeping natural and semi-natural patches within agricultural fields to allow the maintenance of biolog-
ical diversity (‘Wildlife Friendly Agriculture’). We conducted our study in an agroecosystem comprised of
small isolated patches nested within agricultural fields. We trapped reptiles in 13 sampling sites, each of
which included arrays of pitfall traps in a natural patch, in the adjacent wheat field and at the patch-field
edge. We conducted six trapping sessions in the spring – four times before, once immediately after and
once a week after the wheat harvest. Prior to the harvest, we found an intensive movement of Trachylepis
vittata, the most common reptile in our study, from the semi-natural patches into the fields, but negligi-
ble movement in the opposite direction. This pre-harvest directional movement corresponded with
higher abundance of prey (i.e., arthropods) in the wheat field compared to the natural patches in early
spring. The individuals that moved into the fields were adults of better body condition than those remain-
ing in the patch, suggesting that the motivation for movement was habitat preference by individuals with
high prospective fitness rather than the exclusion of subordinates. The population of T. vittata in the
wheat fields and movement across habitats dropped to zero during and after the harvest. Our results pro-
vide strong evidence that the agricultural fields serve as an ecological trap to organisms inhabiting
nearby natural habitats. We suggest that plans for Wildlife-Friendly Agriculture for biodiversity conser-
vation should consider also potential negative effects, such as the ecological trap effect.
Ó2013 Elsevier Ltd. All rights reserved.
1. Introduction
A rapidly growing global human population coupled with an in-
crease in per-capita consumption challenge modern agriculture to
increase productivity in order to meet the increasing demand. This
challenge is being tackled by both an expansion of farming area
and an intensification of agricultural practices. The vast terrestrial
areas affected by agriculture (about 80% globally; MEA, 2005), agri-
cultural intensification, and the cultivation of monocultures are all
expected to cause biodiversity loss (FAO, 2007; Green et al., 2005).
One recent approach to alleviate the negative effects of agriculture
on biodiversity is ‘Wildlife Friendly Agriculture’, which apparently
promotes a balance between food production and conservation by,
among others, leaving natural habitat patches within a heteroge-
neous agricultural landscape (Green et al., 2005). Accordingly,
preservation of natural or semi-natural patches within the agricul-
tural matrix is considered an effective and relatively cheap way to
preserve biodiversity (Aarssen and Schamp, 2002; Benton et al.,
2003; Duelli and Obrist, 2003). In addition to biodiversity conser-
vation, this approach may be beneficial also for farmers because
of the positive ecosystem services that natural habitats provide
for agriculture (Rosenzweig, 2003a,b; Tscharntke et al., 2005;
Bommarco et al., 2013).
However, the proximity of natural habitat patches to agricul-
tural matrix may also affect animal behavior, in general, and hab-
itat selection, in particular (Tscharntke et al., 2012). The selection
of habitats in which to shelter, feed and reproduce can dramati-
cally impact organism fitness. Consequently, most animals have
evolved abilities to sense reliable cues regarding habitat quality
and to move to a better habitat whenever possible (Abramsky
et al., 1985; Pulliam, 1988).
However, the ability to reliably assess habitat quality is often
compromised in human-made environments (Kristan, 2003;
Battin, 2004). Cultivation-related fluctuation in habitat quality
0006-3207/$ - see front matter Ó2013 Elsevier Ltd. All rights reserved.
Corresponding author. Address: Department of Life Sciences, Ben-Gurion
University of the Negev, P.O.B. 653, Beer-Sheva 84105, Israel. Tel.: +972 8 6461350,
mobile: +972 52 3354485; fax: +972 8 6479221.
E-mail addresses: (G. Rotem), (Y. Ziv), (I. Giladi), (A. Bouskila).
Biological Conservation 167 (2013) 349–353
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may attract individuals at certain times and be detrimental at
other times (Best, 1986; Bollinger et al., 1990). The case where
an organism prefers low-quality habitats over other available bet-
ter habitats is called an ‘ecological trap’ (Dwernych and Boag,
1972; Donovan and Thompson, 2001; Hawlena et al., 2010), which
might be considered a special case of source-sink dynamics (Pul-
liam, 1988; Battin, 2004). Such ecological traps may have far-
reaching consequences for the populations in both the low and
the high quality habitats. Robertson and Hutto, (2006) offer three
criteria that define an ‘ecological trap’: ‘‘(1) individuals should have
exhibited a preference for one habitat over another;(2) a reasonable
surrogate measure of individual fitness should have differed among
habitats; and (3) the fitness outcome for individuals settling in the pre-
ferred habitat must have been lower than the fitness attained in other
available habitat’’.
Our study area, the Beit-Nir agroecosystem, is located at the
northern part of Southern Judea Lowlands (SJL), central Israel
E), approximately 50 km southwest of Jeru-
salem (Fig. 1a). Thousands of years of human inhabitance (Ben-Yo-
sef, 1980) and recent intensive agricultural practice formed a
landscape consisting of natural habitat patches at different degrees
of isolation, surrounded by agricultural fields (mainly wheat) vine-
yards and olive groves. The presence of semi-natural patches with-
in this agricultural landscape can potentially host a high diversity
of reptiles. However, these patches are positioned within wheat
fields, a habitat with potentially highly fluctuating quality due to
seasonal cultivation.
Using reptiles, we examine the main hypothesis that the agri-
cultural system serves as an ecological trap, as defined by Robert-
son and Hutto (2006), where many individuals move to and
permanently occupy the agricultural fields, eliminated by the agri-
cultural machinery before or during the reproduction season. We
contrast this hypothesis with an alternative one, stating that the
agricultural system is used for a daily foraging ground by individ-
uals that mainly occupy the adjacent natural habitats.
Our model species Trachylepis vittata [Scincidae] is common
along the eastern Mediterranean basin and in North Africa (Van
der Winden et al., 1995). It is frequently found under stones in
the early morning until the ambient temperature rises above
14 °C. This species also uses rocks as shelters to escape rain and
other extreme weather (Clark and Clark, 1973). It measures
225 mm from snout to tail and feeds on arthropods (Schleich
et al., 1996). Females give birth to live offspring between July
and August (Disi et al., 2001, p. 226).
2. Methods
2.1. Study design and survey protocol
We surveyed reptiles in 13 sampling sites, each including a nat-
ural patch, an adjacent wheat field and the patch-field edge
(Fig. 1b). At each site we installed 40 traps, positioned in two ar-
rays, each comprised of 20 one-liter dry pitfall traps. The traps
were arranged in two parallel lines at distances of 10 m and
15 m on either side of the patch-field edge (Fig. 1b). Additionally,
on the patch-field edge we used a polypropylene multiwall sheet
to build a 100 m-long and 40 cm-high fence (Fig. 1b) that directs
all reptiles’ movement between the natural patch and the agricul-
tural field to passageways located every 20 m along the fence
(Fisher et al., 2008). At those passageways we placed two one-liter
dry pitfall traps, one at each side (total of 10 one-liter dry pitfall
traps along each fence). These sampling methods enabled us to
simultaneously asses the community structure and monitor the
physical condition of reptiles in the natural patch, in the field,
while crossing from the natural patch to field and while crossing
in the opposite direction (Jenkins and McGarigal, 2003).
We trapped reptiles during six sessions throughout the spring
(March to June) – four times before the wheat harvest, immedi-
ately after the harvest and one week later. In each session, traps
were left open for 72 h. Trapped animals were measured (i.e.
weight, snout-to-vent-length, tail length) and identified to species
(and sex when possible; see results). Individuals’ physical condi-
tion was assessed by an index of body condition (IC; Andrews
and Wright, 1994). Initially we intended on using individual
marking to follow the reptiles’ movement. However, as marking
of individuals during the four first sampling sessions resulted in
no recapture at all, this method was not used further on. We re-
leased all captured individuals back to the habitat where they were
captured (in the natural patch or agricultural field) or to the habitat
they were aiming for (in the patch-field edge). We averaged all the
observations from each combination of ‘habitat’ ‘session’ ‘site’
prior to any statistical analysis and used these summarized data as
our replicates, thus avoiding any pseudo-replication.
Incidentally, the pitfall traps also collected arthropods that
were later identified in the lab to their order level. Previous studies
have found a positive correlation between insect abundance and
reptile abundance (Rocha et al., 2008). As all the studied reptile
species were predators, having insects as a dominant component
of their diet, we assumed that arthropod abundance could serve
as a good indicator for habitat quality.
3. Results
Throughout the study, we trapped 352 reptiles, belonging to 9
species. Most of the trapped individuals (271) belonged to our
model species, T. vittata. The vast majority (244) of the 271 individ-
uals of T. vittata, throughout the season and in all habitat types
were adults, 16 were sub-adults (mainly in the pre-harvest ses-
sions only, and in all habitat types) and only 11 were juveniles,
all of which were captured in the natural patch habitat in the
post-harvest session. Although it was sometimes possible to deter-
mine the sex of trapped individuals, in most cases it could not be
reliably done. Therefore, our analysis was not stratified by sex or
by age.
We found a significant effect of both sampling time and habi-
tat (repeated-measures ANOVA, F
(5, 240)
= 10.43, p< 0.001, and
(3, 48)
= 72.46, p< 0.001, respectively) as well as their interaction
(15, 240)
= 9.0643, p< 0.0001) on T. vittata’s abundance (Fig. 2).
T. vittata abundance (Fig. 2) in natural patches remained rela-
tively constant throughout the entire study period. In contrast,
the number of T. vittata found in the wheat field varied. Early in
the season only a few individuals occurred within the field habitat,
but their number increased throughout the spring until the har-
vest. After the wheat harvest, not a single individual was found
within the field habitat. The reptiles’ movement across habitats
was unidirectional with an intensive movement from the natural
patches into the wheat fields in early spring (38 individuals ob-
served). Only two individuals attempted crossing in the opposite
direction throughout the entire season. The very low densities of
other reptile species precluded us from conducting meaningful
analyses at the species level. Nevertheless, the general patterns
for all the rest of the reptile community combined was similar to
the results found for T. vittata. The number of reptiles (excluding
T. vittata) captured per trapping array per session remained con-
stant in the natural patch habitat throughout the season (0.69
and 0.77 for pre-harvest and post-harvest, respectively). It dropped
sharply in the field habitat (from 0.25 individuals in the pre-har-
vest to 0 in the post-harvest). Prior to the harvest, twice as many
individuals crossed from the patch to the field than in the opposite
350 G. Rotem et al. / Biological Conservation 167 (2013) 349–353
direction (0.15 and 0.08 individuals per trapping array per session,
respectively) and no movement was observed in either direction
after the harvest.
Habitat type significantly affected body condition of T. vittata
(Fig. 3; one-way ANOVA, F
(2, 61)
= 33.7, p< 0.05) and we found that
individuals in the natural patches were in poorer physical condi-
tion than those captured in the field or those striving to cross from
the natural habitat to the agricultural field (p= 0.0001, Tukey’s
honestly significant difference post hoc test).
All individuals in the field and those crossing from the natural
patch to the field were adults, whereas juveniles and newborn
were found in the natural patches only.
In early spring arthropod abundance within the wheat fields
was significantly higher compared to that in the natural patches
(in early spring: t-test, t
= 3.791, p= 0.001, SD = 77.173; after
the harvest arthropod abundance within the wheat fields was
not significantly different than that in the natural patches: t-test,
= 1.912, p= 0.07, SD = 72.115).
4. Discussion
Robertson and Hutto (2006) criteria for the existence of an eco-
logical trap include preference for one habitat over another and
lower fitness (measured directly or using a surrogate) in the pre-
ferred relative to the other habitat (see Introduction). The rela-
tively higher insect abundance in the field in early spring may
explain the extreme asymmetrical movement of individuals of
the insectivorous skink, T. vittata, from the natural patches to the
field. Furthermore, the superior body condition of adults crossing
to, or already in the field, relative to those remaining in the natural
patches, clearly indicates that the movement to the habitat with
high food abundance is mainly executed by the individuals in a
better condition, with high potential for reproduction. Meylan
et al. (2002) showed that when movement between patches (i.e.,
dispersal) incurs a high energetic cost, only individuals of better
body condition make an attempt for such movement. Whether or
not this mechanism drove our results, the superior body condi-
Fig. 1. Map of the research area and the study site. (a) White polygons represent natural and semi-natural patches surrounded by agricultural fields, mainly wheat. A diagram
of a trapping array and (b) showing the fence (black line) and the trapping array in each habitat and along the separating fence. A picture of the patch-field edge and the
separating fence is given in c.
Fig. 2. Mean number of Trachylepis vittata individuals per trapping array that was
captured in natural patches, wheat fields and while crossing between these habitats
at different times along the wheat growing season. T. vittata was captured in four
occasions prior to the wheat harvest (Pre-H1–H4 corresponding to end of February,
end of March, Mid April and end of May), immediately after the harvest (Harvest)
and one week later (post-H).
G. Rotem et al. / Biological Conservation 167 (2013) 349–353 351
tioned individuals clearly showed preference to the agricultural
Combined our observations suggest that in early spring, individ-
uals behave according to the expectation of ideal density-depen-
dent habitat selection (Fretwell and Lucas, 1969), i.e., moving to
a higher quality habitat to increase fitness. However, this seem-
ingly optimal habitat selection eventually led individuals to be
trapped in a very poor habitat following the wheat harvest. We
have not found even a single live T. vittata in the field following
the harvest activity. Furthermore, we have not found evidence of
movement of any individual from the field into the patch during
or after the harvest, nor immediately prior to the harvest, despite
a buildup of substantial population in the field at this time
(Fig. 2). Some of the reptiles in the field were presumably killed
by the agricultural machinery; others, exposed to predators like
Corvus monedula,Falco tinnunculus or Circaetus gallicus that accom-
panied the harvest activity, were likely consumed. We indeed
counted more than 20 individuals of each of these predatory birds
following the harvester, apparently collecting prey uncovered by
the harvester (personal observations). This phenomenal scene is
typical to harvesting activity throughout SJL and Israel, and, as
far as we know, also throughout the world.
Much of the results that we obtained, at least early in the sea-
son, could have been generated by a daily movement of individuals
that reside and reproduce in the natural patch and conduct daily
foraging forays into the fields where they benefit from the high
arthropod abundance. If that was the case, we would expect that
at least some individuals that arrived during a trapping session will
be captured on their return to the natural patch. The almost com-
plete lack of such movement, especially in the last session prior to
the harvest, when substantial population was found in the field,
clearly rejects the daily pattern hypothesis. Furthermore, through-
out the spring, the T. vittata population within the agricultural field
grew, which could indicate that individuals that moved from the
natural patches remained in the field and have not used it just
for diurnal foraging. Finally, if daily foraging individuals benefited
from high quality food in the fields, one could expect a negative
correlation between the physical state of individuals in natural
patches and the distance from the high quality field habitat. Using
auxiliary data, where traps were located in different distances from
the patch-field edge (Rotem, 2012), we found no such correlation
(Linear regression, F
= 1.10, p= 0.30, R
= 0.03).
Clearly, our results and observations indicate a large difference
between the fitness provided by the two habitats – while repro-
duction of T. vittata occurs in the natural patch (as evident by the
observation of a few newborns late in the season after the harvest),
the fitness in the fields equals zero (not even a single live T. vittata,
adult or juvenile, in the field following the harvest activity). Fol-
lowing the criteria set by Robertson and Hutto, (2006), we affirm
that the agricultural fields serve as an ecological trap for T. vittata
– better-conditioned individuals show preference for the field, as
indicated by their directionality of movement; the field offers high-
er resource quantity indicating a potential difference in prospec-
tive fitness; and the preferred habitat has eventually a lower
fitness. Although the data enabled us to conduct detailed analysis
for only one common species, the similar patterns observed for
the rest of the community suggest that the implications of the re-
sults may be pertinent for many species, including rare species for
which data is always hard to obtain.
Organisms make decisions regarding their future success based
on currently available information. Most of these decisions are
based on the long process of evolutionary promotion of optimal
habitat selection (Schlaepfer et al., 2002). However, adaptations
for optimal habitat selection that have been shaped by long-term
evolutionary processes may be out of context in cases of anthropo-
genic intervention with the natural environment (Hawlena et al.,
2010). Such intervention, which is usually much faster than almost
any evolutionary process, leads to situations in which organisms
select habitats according to their ‘‘evolutionary knowledge’’
(Battin, 2004), leading, on occasions, to ecological traps (e.g.,
Hawlena et al., 2010). In our case, the wheat field serves as an eco-
logical trap by attracting individuals of better physical condition in
the population to migrate to the seemingly better habitat. These
individuals, of high prospective fitness, find themselves in a very
poor habitat after the harvest, leading to no fitness at all.
The passage of individuals in better physical condition from the
natural patches into the wheat fields, where their fitness is very
low, may further decrease both population size and the quality of
the natural patches’ populations (Schlaepfer et al., 2002). Small
fragmented populations are exposed to inbreeding depression
and genetic drift, which further decrease the population’s genetic
diversity and weaken its ability to cope with both short-term sto-
chasticity (e.g., drought period) and long-term environmental
change (Porlier et al., 2009). The effects of genetic isolation and
the negative qualitative and quantitative effects of ecological traps
on isolated populations in natural patches may be additive, or even
synergistic, increasing the probability of extinction for those popu-
lations. The asymmetric, almost unidirectional, movement across
habitats and the functioning of the wheat fields as an ecological
trap pose a risk, particularly to small patches that share a long bor-
der with the fields relative to their patch area. In such small
patches, the loss of individuals that do not reproduce in the patch
may be detrimental, due to the reduction in the number of individ-
uals available to replace natural mortality in the patch and due to
potentially gradual loss in the quality of the remaining individuals
in the patch.
We believe that the phenomenon of an ecological trap in agro-
ecosystems is not unique to our study area or to our study species,
but may represent an example of a broad phenomenon, probably
found in agricultural areas in many places worldwide (see Bollin-
ger et al., 1990; Shochat et al., 2005). Consequently, we think that
possible risks of ecological traps should be incorporated in the
‘Wildlife Friendly Agriculture’ approach (see Introduction) that is
currently proposed to promote conservation.
This study was funded by Nekudat Hen foundation. This re-
search was also partially supported by a grant from the Israel Sci-
ence Foundation (ISF grant 751/09) to Y.Z. We thank our assistants,
Fig. 3. Index of body condition (IC index) of individuals in the fields, natural
patches and along the fence separating patch and field. The analysis is based on
early-spring trapped adults with intact tail.
352 G. Rotem et al. / Biological Conservation 167 (2013) 349–353
especially Gal Aviad, for their help in the field and the farmers of
Kibutz Bet-Nir for their cooperation.
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... Today, the natural patches consist of Mediterranean garrigue, scrub-steppes, and Maquis. This agroecosystem has been studied in the past in relation to various taxa including beetles (e.g., Yaacobi et al. 2007), spiders (Gavish et al. 2012), and reptiles (e.g., Rotem et al. 2013Rotem et al. , 2016. ...
... Only observed reptiles identified to species level were included in the count. We referred to the total number of observations in the plot as total abundance because, in this study area (Rotem et al. 2013) and in a similar ecosystem (Porat 2011), the number of recaptures between surveys was negligible. When possible, we also calculated species diversity using Fisher's alpha index of diversity (Fisher et al. 1943). ...
... The natural patches, as opposed to the crops we studied, offer a variety of shelters and activity sites for this insectivorous species. Interestingly, Rotem et al. (2013) reported that H. vittatus prefers natural patches over agricultural ones (wheat fields) for reproduction, even though the natural patches might offer higher arthropod abundance. The third most abundant species in the natural patches was the tortoise T. graeca, which is mostly herbivorous and thus associates more in the plots which were located higher on PC1 (i.e., higher live vegetation cover). ...
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Agriculture poses a threat upon wildlife worldwide and particularly to reptiles. However, the effects of many crop types on reptile diversity remain unknown. In this field study, we examined the local effects of two understudied common crop types in Mediterranean regions, intensively cultivated vineyards and intensified-traditional olive plantations, on reptile diversity patterns. We compared measurements of diversity among an array of study plots representing each crop as well as plots in adjacent patches of natural habitat. We developed a new index, the Average Specialization Index, in order to compare the degree of habitat-specialization of the species in the different habitats. Among the habitat types examined, the natural patches were the most structurally heterogeneous and contained the greatest species richness and diversity. In contrast, the intensive vineyards were structurally homogeneous and were uninhabitable areas for reptiles. The more-traditionally cultivated olive plantations were intermediately heterogeneous and provided a unique habitat occupied by a community with a high proportion of reptile species considered to be habitat specialists. Despite showing high abundance and eveness, the reptile community within the olive plantations still contained a lower species richness and diversity compared to natural patches. In light of our results, we recommend implementing a more wildlife-friendly management strategy in landscapes converted to agricultural cultivation.
... The effects of anthropogenic pressures, such as forest fires and intensive land use practices, on reptile populations and communities is therefore well studied (e.g. Ribeiro et al. 2009;Rotem et al. 2013;Guiller et al. 2022). However, a comprehensive evaluation of the effects of environmental features and biotic interactions in Mediterranean human-modified landscapes is poorly understood. ...
... This result can be explained because, in the study area, patches with higher NPP are matched to intensive agricultural activities, where mechanized agriculture (e.g. hay meadows), tilling, input of nutrients from livestock manures and pesticides are present, thus determining a disturbance for the reptile community (Rotem et al. 2013;Guiller et al. 2022). The reptile community instead showed a differential effect for other landscape metrics such as TCD: abundance of P. muralis was positively influenced by tree cover, while the congener P. siculus and the skink C. chalcides were negatively affected by this feature. ...
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Context - Disentangling the effect of environment and biological interaction on community composition with observational data, within the environmental filtering framework, is challenging because the two processes produce non independent results. Objectives - Adopting community N-mixture models with symmetric interactions, we aimed at estimating differential effects of landscape structure and biotic interactions on the local abundance of a Mediterranean reptile community including four lizards (Lacerta bilineata; Podarcis siculus; P. muralis; Chalcides chalcides) and two snakes (Hierophis viridiflavus; Natrix Helvetica). Methods - We sampled reptiles for three consecutive years (2019–2021; 4 surveys/year) on 52 linear transects on a Mediterranean coastal landscape. We analyzed count data by means of a multi-species N-mixture model with symmetric interactions. Interactions within pair of species were estimated from the residual correlation of their realized abundances, after accounting for four landscape features: landscape heterogeneity calculated from land cover data, edge density of woody vegetation patches, tree cover density, net primary productivity. Results - Most species displayed very low detection probability (p ~ 0.10). All species responded with different intensity and sensitivity to landscape predictors. Two biological interactions resulted significant: L. bilineata and P. siculus showed a positive interaction, while P. muralis and C. chalcides displayed a negative interaction. Conclusions - Using community N-mixture models we demonstrated that, also with observational data obtained from a realized community, partitioning the filtering process of the landscape from the one of biotic interactions is possible.
... Lardner 2006, 2009;Ribeiro et al. 2009): groups are particular sensitive to agricultural activities (Dürr et al. 1999), such as the use of pesticides (Brühl et al. 2013). Further, agricultural lands may even serve as ecological traps: individuals selecting seemingly optimal habitats can eventually end trapped in low-quality habitats, for example after harvest (Rotem et al. 2013). ...
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ContextEvaluating herpetofauna presence and the species-specific and species richness patterns in response to agricultural landscape features is essential for understanding the herpetofauna decline in agricultural landscapes.Objectives This work aimed to explore how different categories, extent and heterogeneity of crops affect herpetofauna distribution and diversity patterns at different spatial resolutions: UTM 50 km2, UTM 10 km2 and GPS coordinates.Methods Using presence-only data from online repositories we documented the occurrence of European amphibians and reptiles in crops and quantified crop extent and heterogeneity in 50 and 10 km2 grid cells, and in the recorded presence locations. We used logistic regressions to test the effect of crop extent on species occurrence and calculated the proportion of species showing a significant response to each crop category. We analysed species richness patterns with generalized additive models against crop extent, crop heterogeneity and crop categories extracted at GPS locations, as fixed effects.ResultsWe recorded 71 amphibian and 143 reptile species at 50 and 10 km2 spatial resolutions, and 58 amphibian and 108 reptile species at GPS resolution. Our results showed that amphibian and reptile species presence and richness are influenced by crop category, extent and heterogeneity and that spatial patterns were scale dependent. Species richness of both amphibians and reptiles was generally negatively correlated with crop extent but was enhanced by crop heterogeneity.Conclusion Our results provide useful information for future risk assessment of herpetofauna and conservation efforts to restore or sustain herpetofauna biodiversity in agricultural systems across Europe. We stress that the scale of landscape management may lead to contrasting outcomes.
... Here, we analysed how hourly movement rate, inter-day distance and activity area size vary according to land cover type (farmland, tree patches, grassland), time of year, animal body size and sex. We predicted high hourly and inter-day movement rates by lizards inhabiting farms compared to animals in tree patches and grasslands, because tree and grassland areas may offer more cover and abundant prey than harvested farms (Gehring & Swihart, 2004;Rotem et al., 2013). Conservation strategies often aim to mitigate the impacts of fragmentation on animals through restoration and protection of core habitats (Hansen et al., 2020). ...
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Agriculture is one of the greatest threats to biodiversity worldwide, but knowledge of how agriculture modifies animal movement, which is crucial for survival, is limited. Here, we examined the effect of landscape composition on the movements of the oriental garden lizard Calotes versicolor in agricultural landscapes of north-central Pakistan. We radio-tracked 32 individuals over 5 months to determine whether land cover type (farmland, tree patches, grassland) influences hourly movement rate, inter-day distance moved, and activity area size. We found that hourly movement rates were higher in tree patches compared to grasslands, and higher when animals moved between land cover types rather than within individual land cover types. Activity area size and movement rates became smaller as the season progressed, but they did not differ according to animal sex or body size. Habitat selection analysis showed that lizards preferred tree patches, avoided farms, roads, water bodies and human dwellings, and used grasslands in proportion to availability. When lizards used farmlands, they were found in field margins 85% of the time. Our results emphasize the importance of treed areas as reptile habitat in these highly modified agricultural lands. Agricultural intensification that reduces the availability of tree patches and field margins will likely reduce the extent to which lizards can use the landscape by removing preferred habitat. Maintaining tree cover and small fields with field margins should promote the coexistence of wildlife conservation and food production in agricultural landscapes. © 2022 The Authors. Animal Conservation published by John Wiley & Sons Ltd on behalf of Zoological Society of London.
... The main vegetation types are semi-steppe Mediterranean scrubland and grassland (Giladi et al. 2011). Thousands of years of human inhabitance and recent decades of intensive agricultural practices formed the landscape into a patch-matrix mosaic, with remnant natural patches embedded in agriculture fields, mainly wheat and legumes (Giladi et al. 2011;Rotem et al. 2013). ...
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Context Natural habitat patches can mitigate the negative effects of agriculture on biodiversity. Local communities within natural patches are connected by dispersal and affected by multi-scale processes. Network theory enables to analyze metacommunity structures of different groups of species, such as common and rare species, and provides tools to prioritize the habitat patches. Objectives We ask what are the local and landscape determinants of common and rare species diversities and whether the relative importance of the patches within the networks is similar for common and rare species. Methods We sampled arthropod communities within natural patches in a fragmented agroecosystem of the Southern Judea Lowlands, Israel. We classified Coleoptera, Araneae, and Hemiptera taxa into common and rare species and constructed a metacommunity network for each group of species. Results For Coleoptera and Hemiptera the association of patch connectivity is stronger with rare species than with common species diversities, suggesting that landscape determinants are more dominant in shaping rare than common species assemblages. Moreover, the spatial scale at which patch connectivity affects common and rare species differs between taxa. By comparing the relative importance of patches within the networks, we found a high correlation between common and rare species in each taxon. However, several patches diverge from this trend of similarity. Conclusions This study emphasizes the importance of multi-scale determinants in shaping ecological communities at agroecosystems and stresses that common and rare species are distinctive groups of species that should receive explicit consideration in conservation management and planning.
... Lardner 2006, 2009;Ribeiro et al. 2009), both groups being particular sensitive to agricultural activities (Dürr et al. 1999), such as the use of pesticides (Brühl et al. 2013). Further, agricultural lands may even serve as ecological traps (Rotem et al. 2013). ...
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Context To understand the herpetofauna decline in agricultural landscapes with herpetofauna presence and evaluating the species-specific and species richness patterns in response to their features. Objectives This work aimed to explore how different crop categories (i.e. agroforestry, irrigated, dry and woody crops and pastures), crop extent and heterogeneity affect herpetofauna distribution and diversity patterns at two different spatial resolutions, UTM 50km2 and UTM 10km². Methods We documented the occurrence of European amphibians and reptiles in crops and quantify crop extent and heterogeneity in 50km² and 10km2 grid cells. Results We recorded 72 amphibian and 142 reptile species at UTM 50 km2 and UTM 10 km² grids. The geographic location of peaks and troughs of crop extent and of species richness at UTM 50km² did not coincide with those at UTM 10km². Our results showed that amphibian and reptile species presence and richness are influenced by crop category, extent and heterogeneity and that spatial patterns were scale dependent. Species richness of both amphibians and reptiles was generally negatively correlated with crop extent but was enhanced by crop heterogeneity. Conclusions Our results provide useful information for future risk assessment studies of herpetofauna, such as to identify candidates (i.e. “representative species”) for pesticide effect field studies or for studies of risk refinement though radio-tracking.
... Human-induced rapid environmental change is known to interfere with animals' abilities to assess the fitness value of novel habitats, and optimizing habitat choice for one component of fitness could cause rapid population declines that jeopardize species persistence (Robertson et al., 2013). For example, an individual that prefers crop fields or field margins to optimize food resource availability may also become more vulnerable to predators or management disturbances and experience increased mortality (Rantanen et al., 2010;Rotem et al., 2013). Farms may also act as low-quality population sinks, where declining populations are only sustained by immigrants from high-quality natural habitats (Pulliam, 1988;Holt, 2011). ...
Farmland diversification practices are sometimes considered a win-win for agriculture and biodiversity, but most studies rely on species richness, diversity, or abundance as a proxy for habitat quality. Biodiversity assessments may miss early clues that populations are imperiled when species presence does not imply persistence. In contrast, physiological stress indicators may help identify low-quality habitats before population declines occur. We explored how avian stress indicators respond to on-farm management practices and surrounding seminatural habitat (1km radius) across 21 California strawberry farms. We then asked if commonly used biodiversity metrics correlate with stress responses in wild birds. Specifically, we used ∼1,000 blood and feather samples, as well as body mass and wing chord measurements mostly from passerines, to test the effects of diversification practices on four physiological stress indicators: heterophil to lymphocyte ratios (H/L ratios), body condition, hematocrit values, and feather growth rates of individual birds. We then tested the relationship between physiological stress indicators and species richness, abundance, occurrence, and diversity, derived from 285 bird point count surveys. After accounting for other biological drivers, we found that landscape context mediated the effect of local farm management on two stress indicators (H/L ratios, body condition). Local diversification practices were associated with reduced stress experienced by individual birds in intensive agricultural landscapes but increased it in landscapes surrounded by more seminatural habitat. We also found that feathers grew more slowly in landscapes dominated by strawberry production, suggesting that nutritional condition is lower in these landscapes. We found scant evidence that species richness, abundance, occurrence, or diversity metrics were correlated with the physiological stress experienced by individual birds, suggesting that reliance on these metrics may obscure the impacts of management on species persistence. More broadly, our findings underscore the importance of considering landscape context when designing local management strategies to promote wildlife conservation. This article is protected by copyright. All rights reserved.
... For example, farming practices -especially those traditionally managed-generate human-made ponds, which can provide an adequate environment for many amphibian species (Hartel et al., 2010;Knutson et al., 2004;Lescano et al., 2015). For reptiles, some evidence indicates that species richness of assemblages is not significantly modified in agricultural landscapes (Suazo-Ortuño et al., 2008), and such response maybe related to a potential increase in the abundance of prey for reptiles (Rotem et al., 2013). ...
Human land-use changes represent the most important drivers of biodiversity loss, and amphibians and reptiles represent the most threatened groups of vertebrates globally. However, today there is a general lack of knowledge and little consensus on how land-use changes affect amphibians and reptiles. In order to fill this gap, here we conduct the most comprehensive systematic quantitative review of primary research to date. By means of hierarchical meta-analyses we assessed the effects of the most common land-use changes (agriculture, cattle-raising, urbanization, deforestation, silviculture and selective logging) on the richness of amphibian and reptile communities. Our results show that almost all of the analyzed types of land-use changes have negative effects on these groups, but with different degree of magnitude. We also show that the time elapsed in disturbed conditions does not ameliorate the effects on species richness, indicating a low recovery capacity of herp communities. Another important finding is that the richest communities are the most negatively affected ones, varying the response according to the type of biome. Our synthesis provides updated empirical evidence indicating that current prevalent human land-use changes strongly reduce the richness of amphibian and reptile species as well as revealing important knowledge gaps in certain biomes of the world. These results should help providing a basis for the development of future research and contextualizing the need for effective conservation measures for these two vertebrate groups.
Conservation behavior assists the investigation of species endangerment associated with managing animals impacted by anthropogenic activities. It employs a theoretical framework that examines the mechanisms, development, function, and phylogeny of behavior variation in order to develop practical tools for preventing biodiversity loss and extinction. Developed from a symposium held at the International Congress on Conservation Biology in 2011, this is the first book to offer an in-depth, logical framework that identifies three vital areas for understanding conservation behavior: anthropogenic threats to wildlife, conservation and management protocols, and indicators of anthropogenic threats. Bridging the gap between behavioral ecology and conservation biology, this volume ascertains key links between the fields, explores the theoretical foundations of these linkages, and connects them to practical wildlife management tools and concise applicable advice. Adopting a clear and structured approach throughout, this book is a vital resource for graduate students, academic researchers, and wildlife managers.
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State of Nature Report 2018 by HaMaarag, Israel’s State of Nature Assessment Program, presents trends and processes in the state of Israel’s ecosystems, and opens a door to the ecological data collected in them. The report is part of a series of publications by HaMaarag, dealing with the state of nature in Israel. The main sources for this report are data from Israel’s National Biodiversity and Open Landscapes Monitoring Program and in-house analysis of spatial data, with additional out-sourced monitoring data. The main goal of the State of Nature Report is to promote the consolidation of strategies, and the development of conservation interfaces, for the advancement of sustainable management of open landscapes and natural resources in Israel.
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Processes that affect ecological community measurements, such as abundance, species richness or species diversity, form the framework of ecology. For years these processes were investigated by examining local factors (explanatory variables) that may affect the relationship between individuals or species on a local scale. Over the last two decades, due to the rise of advanced scientific theory and practice, new computational and statistical approaches have been developed, allowing ecologists to examine community structure and measurements using several scale-dependent variables and processes. Despite much research conducted in this field, reptiles as a biological group have been somewhat neglected compared to other groups (e.g. birds, insects, rockpools). Over the years, various studies have been conducted on the structure of ecological communities within agricultural systems, using diverse approaches, including advanced methods of spatial ecology. However, contiguous farmland is rarely spread over a sharp climatic gradient, so the effect of such a gradient on community structure within an agricultural system is currently understudied. In addition, in cases where a climatic gradient exists, it is usually accompanied by changes in elevation, ground composition, and geology, and, as expected, in the agricultural activity itself. The study area for this thesis, the Southern Judea Lowlands, is characterized by a very sharp climatic gradient over a short distance, with no significant change in elevation, soil, geology, human history or agricultural activities. This PhD thesis examines scale-dependent variables that affect the reptile community within natural patches in the fragmented agricultural system of the Southern Judea Lowlands. The first chapter addresses the effect of different spatial scale variables on the reptile community located in natural patches within an agricultural matrix. Three 3.2×4 km land units were chosen, located from north to south – Galon, Lachish and Dvir. These land-units reflect the north-south climatic gradient that exists at the landscape scale. Patches of varying size, shape and spatial configuration were identified within the land-units. Within these patches, I marked 100×50 m equal-sized plots which were used for sampling reptiles. This sampling method allowed me to examine how a series of variables (e.g. plot heterogeneity, patch size and spatial configuration), which operate at different spatial scales and may be related to different ecological processes, affect the reptile community. By using an AICc-based (Akaike Information Criterion with correction for finite sample sizes) model selection approach, I examined which variables most affect community structure. The models that offered the best explanation for the three community measurements – abundance, species richness and species diversity – were all multiple scale models. However, all three community measures were strongly affected by local scale variables which suggested a strong influence of local hetrogeneity on reptile communities. Moreover, for all three community measures, both grazing and climatic gradients together were found to be an important variable, which indicates the significance of this combined environmental phenomenon. The second chapter deals with one of the most common agricultural activities within my research area -- seasonal grazing of sheep (Ovis aries) and cattle (Bos primigenius). Grazing takes place mainly in the stubble after harvest, but herds also find natural patches located within the agricultural matrix. Previous studies have examined the effect of domestic animal grazing on reptile communities, but few of these have examined the integrated effects of grazing and climate, especially within a similar area. In Chapter 2, I examine the combined effect of grazing and climatic gradient on the reptile community of the Southern Judea Lowlands with an additional site to the south – Rahat. I list the proportion of species according to their biogeographical origin. The results indicate a decrease in the percentage and relative abundance of Mediterranean species and an increase in the percentage and abundance of desert species with decreasing precipitation. The effect of grazing itself also changed according to the location of the plot along the climatic gradient. Within the Galon land-unit, which belongs to the Mediterranean climate, grazing was found to increase plot heterogeneity and species richness. In contrast, in the southern area, near Dvir, a negative effect of grazing on plot heterogeneity and species richness was found. At Dvir, grazing was also found to affect community composition. Mediterranean-oriented species richness was negatively affected by grazing intensity. In contrast, arid-oriented species richness was positively related to grazing intensity at Dvir. Apart from grazing, the study area is also characterized by the presence of vast wheat fields. In the third chapter of the work I address the effect of wheat fields on the reptile communities. I chose to focus on plots located in the center of wheat fields which were all concentrated in the northern land-unit Galon, in order to avoid in this analysis the impact of the climatic gradient. In addition, due to the paucity of observations of other species, this part of the study focused on the lizard Bridled Mabuya (Trachylepis vittata) only. Arthropod abundance found in the early spring within the wheat fields was significantly higher than in natural patches. In addition, I found a significant movement of reptiles from natural patches to the wheat fields, but very little in the opposite direction. The physical condition of the individuals who left the natural patches for the fields was significantly better than that of the individuals who remained in the natural patches. Finally, no individuals were found within the wheat fields after the harvest in contrast to the natural patches. These results indicate that wheat fields act as an ecological trap for T. vittata. This third chapter has been accepted for publication in the journal Biological Conservation. In conclusion, the results of this work suggest that the reptile community within a fragmented agro-ecosystem is affected by many scale-dependent ecological processes. The results also suggest that the presence of a reptile community within an agricultural area is affected by the type of agricultural crop and other agricultural practices. My research highlights the need to consider various scale-dependent ecological variables, as well as the type of agricultural activity, when investigating ecological communities within an agricultural area.
Conservation tillage fields may consititue 'ecological traps' for nesting birds because these fields appear to provide more suitable nesting cover than more heavily tilled fields but nest disturbance may still be frequent enough to cause poor nesting success. -from Author
Ecological traps, poor-quality habitat that nonetheless attract individuals, have been observed in both natural and human-altered settings. Until recently, ecological traps were considered a kind of source-sink system, but source-sink theory does not model maladaptive habitat choice, and therefore cannot accurately represent ecological traps or predict their population-level consequences. Although recent models of ecological traps addressed this problem, they used patch-based models containing only two habitats that were very different from one another, but were internally homogeneous. These sorts of patch models may not apply to many real populations, and using them for populations in landscapes with mosaic or gradient habitat structures may be misleading. I developed models that treat source-sink dynamics and ecological traps as special cases of a single process, in which the attractiveness and quality of the habitat are separate variables that can be either positively or negatively related, and in which habitat quality varies continuously throughout the landscape. As expected, sinks are less detrimental to populations than ecological traps, in which preferential use of poor habitat elevates extinction risk. Furthermore, ecological traps may be undetected, and may even appear to be sources, when population sizes are large, but may still prevent recovery in spite of the availability of high-quality habitat when populations drop below threshold levels. Conservation biologists do not routinely consider the possibility that apparent sinks are actually traps, but since traps should be associated with the rapidly changing and novel habitat characteristics primarily produced by human activities, ecological traps should be considered an important and potentially widespread conservation concern.
Studied habitat selection in six rodent species that occur in sandy or rocky areas of the Israeli desert using two complementary quantitative techniques. A distribution method for detecting habitat selection takes cognizance of density dependence but cannot establish what properties of the environment are being selected by the species. This and the traditional regression method were equally successful in discriminating between rodent species that exhibit selection and those that do not. Only the regression method can suggest the habitat variables that are actually preferred by a species. Either temporal or spatial variation in the data may result in backward regressions (indicating the right variable but in the wrong direction), because populations at low densities may be restricted to their best habitats. At high densities, however, populations utilize both preferred and marginal habitats. When both temporal and spatial variation exist, the regression method may fail altogether to detect habitat selection even when it exists. The distribution method does not suffer from this weakness.-from Authors
Mabuya vittata is a highly polymorphic diurnal lizard, occurring in high densities (20-160/ha) in the Goksu Delta in southeastern Turkey. Two dorsal pattern types were distinguished, uniform or effectively uniform and striped. In the hills and dunes 93% (n = 311) of the adult animals was uniform and in the agricultural parts of the delta 73% (n = 175) was striped. 74% (n = 464) of M. vittata was found in the herb layer. In the hills and dunes the relative share of grasses is low in this layer, in the agricultural area grasses have a high coverage. Strong correlations were found between the striped pattern and high grass coverage, and between the uniform pattern and a low grass coverage, assuming disruptive selection by visually hunting predators
The species pool hypothesis is applied here to the interpretation of ‘hump-shaped’ (unimodal) species richness patterns along gradients of both habitat fertility and disturbance level (the habitat templet). A ‘left-wall’ effect analogous to that proposed for the evolution of organismal complexity predicts a right-skewed unimodal distribution of historical habitat commonness on both gradients. According to the species pool hypothesis, therefore, the distribution of opportunity for net species accumulation (speciation minus extinction) should also have a corresponding unimodal central tendency on both habitat gradients. Two assumptions of this hypothesis are illustrated with particular reference to highly fertile, relatively undisturbed habitats: (i) such habitats have been relatively uncommon in space and time, thus providing relatively little historical opportunity for the origination of species with the traits necessary for effective competitive ability under these habitat conditions; and (ii) species that have evolved adaptation to these habitats are relatively large, thus imposing fundamental ‘packing’ limitations on the number of species that can ‘fit’ within such habitats. Based on these assumptions, the species pool hypothesis defines two associated predictions that are both supported by available data: (a) resident species richness will be relatively low in highly fertile, relatively undisturbed contemporary habitats; and (b) species sizes within regional floras should display as a right-skewed unimodal (log-normal) distribution. The latter is supported here by an analysis of data for 2,715 species in the vascular flora of northeastern North America.