Infrastructure development can lead to both increased poach- ing and agricultural expansion while a blockage of migration may also force animals into more marginal habitat. In Mongo- lia, the Ulaanbaatar-Beijing railway is believed to be the most important causal factor in closing the historic east-west mi- gration of Mongolian gazelle (Lhagvasuren & Milner-Gulland 1997; Ito et al. 2005).
Many migratory species die attempting to cross fences and bar- riers. Unfortunately, building roads and railroads may result in avoidance (Lian et al., 2008) and likely reduced crossings, as is well documented for numerous species. A famous photo launched in 2006 revealed a group of antelopes crossing under the train, but the photo was later revealed to be a fake (Qiu, 2008; Yang and Xia, 2008). Indeed, new satellite data suggest that while Chiru antelopes still cross the Qinghai-Tibetan railway and the Golmud-Lhasa highway to reach and return from their calving grounds, the animals spend 20–40 days looking for passages and waiting (Xia et al., 2007; Buho et al., 2011). The infrastructure has likely led to serious delays in their movement to and from the calving area, which in turn may affect productivity and survival.
such as by displacement of migratory species, calving grounds or wintering ranges, which may also lead to reproductive col- lapse, genetic isolation, increased predation risk or starvation.
The veterinary fences across Botswana and Namibia to halt the spread of foot-and-mouth disease to domestic cattle caused the death of tens of thousands of wildebeest, which were no lon- ger able to reach their water sources. The fences also had an impact on other migratory wildlife including zebras, giraffes, buffalo, and tsessebes (Mbaiwa and Mbaiwa, 2006). Some of the animals have been observed walking along the fences try- ing to cross, similar to delays observed in Central Asia and China following construction of railroads and border fences (see below). This, in turn, makes them highly vulnerable to predators and poachers.
Indeed, major migratory ungulate populations in many parts of southern Africa and Central Asia have dropped by 50–90 per cent in the past half century as migrations have been impeded or blocked (Mbaiwa and Mbaiwa, 2006; Bolger et al., 2008).
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Development of livestock and fencing, even livestock within protected areas, also affect the wildlife and migrations, includ- ing Tibetan gazelle (Procapra picticaudata), Goitered gazelles (Gazella subgutturosa), and Kiang wild ass (Equus kiang) (Fox et al., 2009).
Habitat loss and often subsequent competition and poaching caused by agricultural expansion into the most productive sea- sonal habitats, along with halting or delaying or hindering mi- grations, is a primary threat to many migratory ungulate popula- tions. In Masai Mara, Kenya, a decline of 81 per cent between the late 1970s and 1990s in the migratory wildebeest (Connochaetes taurinus) population has been reported (Ottichilo et al. 2001; Bol- ger et al., 2008). Populations of almost all wildlife species have declined to a third or less of their former abundance both in the protected Masai Mara National Reserve and in the adjoining pas- toral ranches (Ogutu et al., 2011). Human influences appeared to be the fundamental cause (Ogutu et al., 2011). Other reports have shown major declines in wildebeest in i.e. Tarangire in Tanzania that declined by 88 per cent over 13 years (Tanzania Wildlife Re- search Institute 2001; Bolger et al., 2008). Increased anti-poach- ing training and enforcement, including training of trackers and improved crime scene management to secure evidence for
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