4.4 Increased individual vigilance with tourism
Our study confirmed former studies (Wang et al., 2009; Che et al., 2018)
that adults took the responsibility of anti-predator scanning with
significant higher alert time expenditure and duration. Wildlife
decrease individual vigilance and benefit from foraging by gathering in
big flocks (Pulliam, 1973; Kong et al., 2020), but interspecific
conflicts also increase with group size (Pulliam, 1973; Caro, 2005), and
juveniles are more vulnerable to conflicts. So, in winter, we could
observe many family groups (2 adults with 1-2 juveniles) forage
separately from other large groups (Liu et al., 2008), so as to keep
>80% of time in foraging for young birds (Wang et al.,
2009). Whereas adults in family groups have to spent
~6% more time than adults in large groups in vigilance
instead of foraging (Wang et al., 2009). Interestingly, in order to
conquer high predation risk faced by family groups, both individual
vigilance sequence organization and inter-scan intervals of black-necked
cranes are randomly distributed throughout the year (Li et al., 2017),
making vigilance bouts more unpredictable than predators could not
initiate successful attack. Compared with other wintering grounds of
black-necked cranes in China, including those at Caohai wetlands in
Guizhou province (vigilance: 12.59-16.52%; Li and Ma, 1992), Napahai
wetlands in Yunnan (vigilance: 11.74-17.05%) and Lhasa in Tibet
(vigilance: 17.8-21.0%; Che et al., 2018), black-necked cranes in
Dashanbao spent most time allocation to vigilance (27.30-31.28%); even
higher than former research conducted here in 2008 (vigilance:
15.6-21.4%; Kong et al., 2008) before visitation opens for public
tourists. Black-necked cranes in our study area are facing equivalent
disturbance to the birds in Daqiao wetland (vigilance: 27.9±16.5%; Kong
et al., 2020) with a large human density of 135 residents per square
kilometers, about 80km away from Dashanbao. Similarly, individual
vigilance of cranes in our study (observer distance) and in Daqiao are
significantly affected by human disturbance (Kong et al., 2020). We
believe that the predominant landscape of vast marshes in Napahai and
Caohai wetlands, which the help of avoidance of human access to crane
habitats contributed the lower anti-predator scans. Wintering habitats
utilized by cranes in Dashanbao and Daqiao are farmland (Kong et al.,
2018). From a historical view, our study also demonstrated that the
explosive expands of nature-based tourism cause new threats to the
threatened black-necked cranes (Li et al., 2014). So, we argue that it
is likely that there is strong interference from tourism caused
coordinated vigilance in black-necked cranes in our study.