Municipalities, UPP’s, and Number of Visits
Data from 79 municipalities (2014: 38, 2015: 63, 2016: 39, 2017: 36); 1,259 visits (2014: 303, 2015: 466, 2016: 261, 2017: 229) and 1,229 UPP’s were analyzed. Number of UPP’s and Number of visits were the same since UPP’s were only visited once per year. Municipalities with greatest number of visits were Tzucacab (105), Izamal (90), and Buctzotz (82), whereas Abala, Acanceh, Kaua, Progreso, Samahil, San Felipe, Seye, Teabo, Ucu, and Yobain were visited only once.
Vampire bat abundancy
9,185 vampire bats were captured, having the greatest number of vampire bats captured in 2015 and the smallest number captured on 2014 (Table #1). On average, 2,296 vampire bats were captured every year, 116 per municipality and 7 per UPP. Similarly to Costa and Esberard (2011) findings; municipalities with greater number of visits had greater abundancy, except Tizimin municipality, which ranks 5th on number of visits and 140 individuals were captured, and Yaxcaba, where 218 bats were captured in 4 visits. MacSwiney et al., (2007) suggested that D. rotundus is the second most abundant species in Cenotes located on grazing paddocks from livestock landscapes in Yucatan and, according to Ruiz et al., (2007), the Cenotes are the refugia for 85% of bats in Yucatan, finding most of cenotes in the Eastern Coastal and Eastern region of the Yucatan State. Nevertheless, in our study, Municipalities that registered the greatest number of vampire bats were Izamal (1.255), Sudzal (715), Buctzotz (673), and Tunkas (621) (Fig. 1), which are in the Central region of Yucatan, except for Buctzotz, which is located in the Eastern Coastal region. Smallest abundancies were found in Progreso (1) and Yobain (1), both located in the Coastal region of Yucatan. Municipalities with greatest and smallest number of individuals per year are shown in Table 1.
Despite Tizimin municipality and in general terms, the Eastern region of Yucatan have a greater proportion of cattle and cave-like cenotes, than other regions (INEGI, 2007; Anderson, S. et al, 2012; Ruiz Silva, 2007), according to our findings, Izamal municipality and surrounding municipalities in the Central region, have a greater abundance of vampire bats. In addition, Izamal, registered the greatest number of cattle attacked for years 2016 and 2017 and in general, for the full observation period. It is suggested that in Yucatan there are from 7,000 to 8,000 cenotes, however, there are still some cenotes and caves not registered, therefore refugia availability (cave-like cenotes) in Central region for vampire bats might be greater than expected, not considering availability of other refugia either natural or artificial. In addition, factors such as distance from refugia to night resting area for preys, density of cattle, and level of human interference, might play an important role in vampire bat abundancy and incidence of cattle attacks (Andrade et al., 2015; Orlando et al., 2019; Lanzagorta et al., 2020) therefore, behavior of these variables per municipality and UPP, besides cattle abundancy and availability of refugia need to be analyzed.
Attacks to cattle
In Yucatan, 37,019 head of cattle were inspected, 5,450 presented at least, one bat’s bite, representing 14.72% of total cattle inspected, whereas in Ecuador, Orlando et al., (2019) reported 23.3% of 1,195 cattle to be attacked by vampire bats. Our results suggest that, on average, 4 head of cattle are attacked every night, considering 79 municipalities with 1,229 UPP and 4 years of observations. In terms of head of cattle attacked by municipality during the full observation period, Izamal (509), Tzucacab (467), Tunkas (456), and Sudzal (376) presented highest number of head of cattle attacked, whereas Progreso (1), San Felipe, Santa Elena and Ucu (2) presented the lowest records (Figure #2). Even though the greatest number of cattle is found in the northeast region of Yucatan (INEGI, 2007), in this study, the greatest number of cattle attacked was in the central region of the State. This is consistent with the study done by Moya et al., (2015) in Bolivia, where they found that the largest incidence of cattle attacks was not observed in the locations with the largest number of cattle.
Excluding municipalities where only one head of cattle was recorded and it was attacked, the greatest proportion of cattle attacked was recorded in Suma (2014, 6/10), Yaxcaba (2015, 38/38; 2016, 60/60) and Kinchil (2017, 16/16). During the full observation period, Kaua, Yaxcaba and Seye presented the greatest percentage of cattle attacked (100%, 100%, and 59% respectively). It is important to mention that in these municipalities, the number of cattle was small, similar to what Turner (1975) reported, who suggests that locations with less cattle, frequency of attacks is greater since vampire bats have to feed from the same individuals. In the same way, Moya et al (2015) found that in pens with less cattle, the incidence of attacks was higher. Moreover, it has been found that in less fragmented zones, where abundancy of wild animals is greater, incidence of attacks to cattle is smaller (Torres et al., 2014). On the other hand, Orlando et al (2019) suggest that vegetation could play an important role on the incidence of vampire bats attacks. Same authors (Orlando et al., 2019) found greater number of attacks in places with high vegetation index, and in a study in Sao Paulo, Brazil (Gomez et al., 2010), it was observed that as the distance from cattle to unfragmented woods and grazing areas decreases, the incidence of vampire bat attacks increases.
Table 1
Vampire bat and cattle abundancy and number of cattle attacked from Jan 2014 to December 2017.
Variable
|
2014
|
2015
|
2016
|
2017
|
CATTLE POPULATION
|
8,854
|
12,059
|
9,314
|
6,792
|
NUMBER OF CATTLE ATTACKED
|
1,093
|
1,768
|
1,578
|
1,011
|
PROPORTION OF CATTLE ATTACKED
|
21.1%
|
20.0%
|
21.5%
|
20.5%
|
VAMPIRE BAT ABUNDANCY
|
1,667
|
2,819
|
2,605
|
2,094
|
Table 2
Municipalities with greatest and smallest number of vampire bats and cattle attacked per year. T = Total, A = Attacked
Year
|
Municipality with > nº of vampire bats
|
Municipality with < nº of vampire bats.
|
Municipality with > nº of cattle attacked
|
Municipality with < nº of cattle attacked
|
2014
|
Sudzal (212)
|
Cansahcab (1), Kopomá (1)
|
Tzucacab (T: 714, A: 109)
|
Cansahcab (T: 1, A: 1),
Kopomá (T: 30, A: 1)
|
2015
|
Buctzotz (282)
|
Progreso (1), Yobaín (1)
|
Sudzal (T: 390, A: 184)
|
Baca (T: 23, A: 1),
Dzilam González (T: 19, A: 1), Progreso (T: 240, A: 1)
|
2016
|
Izamal (363)
|
Cacalchen (1)
|
Tunkás (T: 856, A: 218)
|
Cacalchén (T: 22, A: 1),
Kantunil (T: 64, A: 1),
Muna (T: 12, A: 1)
|
2017
|
Izamal (666)
|
Muna (2)
|
Izamal (T: 1042, A: 261)
|
Dzemul (T: 7, A: 1)
|
ANOVA AND CORRELATION ANALYSIS
Despite some studies suggest annual changes in vampire bat abundancy (Costa and Esberard, 2011), according to our results of ANOVA and Tukey tests, there is no statistical effect of “year” as a factor for the variables analyzed (Fig. 3), similar to Rocha and Dias (2020) observations, who did not find differences in vampire bats captured in consecutive years.
High positive correlation was found between vampire bats captured and number of cattle heads attacked (Fig. 4), which corresponds with Moya et al., (2015) study, who observed that in places with high vampire bat abundancy, the incidence of attacks was higher. In addition, a positive correlation between total cattle and number of vampire bats captured (Fig. 4) was found. This coincides with Becker et al., (2018) findings. Past studies (Schmidt et al., 1971; Turner, 1975) suggest that incidence of attacks is not related to abundancy of mammal preys, however, our work suggests a positive relation between total number of cattle and the number of cattle attacked (Fig. 4), similarly, Orlando et al., (2019) found a correlation between number of cattle attacked and herd size, and between number of bites and number of cattle attacked.