尽管目前棕颈鹭没有被列入濒危名单，但由于寿命较长，繁殖率较低，它们的种群数量亦面临着严重的威胁。
Although the birds aren't listed as endangered, threats to their populations can pose serious risks, because the species has a long life span and a low reproductive rate.
值得注意的是，松鸡数量必需管理：如果荒野中松鸡过度繁殖，这种鸟类就会得病，导致种群数量暴跌。
Significantly, grouse need to be managed: if moors become over-populated the birds may become diseased and populations can crash.
当一个物种的种群数量稀少而又不得不近亲繁殖时，灭绝就会发生。
And this is what happens with small populations and inbreeding of close relatives.
这种单细胞生物吃糖，而且繁殖迅速——如果有足够的食料，他们的种群数量可以每九十分钟增加一倍。
This single-celled fungus feeds on sugars and reproduces frequently—if it has enough to eat, a culture can double in population in 90 minutes.
而这些数量稀少的老虎分散在13个国家，其中4个国家的虎不再有可繁殖的种群了。
And these are scattered thinly over 13 nations, four of which no longer have viable breeding populations.
种群的数量季节消长主要是繁殖和死亡两因素相互作用的结果。
Reproduction and mortality are two primary factors to affect population quantity dynamic.
只考虑这些不确定的繁殖能力，灭绝不太可能如果个体的数字在一个种群数量超过50并且种群数量在增长。
Taking only this uncertainty of ability to reproduce into account, extinction is unlikely if the number of individuals in a population is above about 50 and the population is growing.
林地鼢鼠种群是通过雌雄鼠的数量关系来调节种群繁殖。
The population breeding was regulated by the quantitative relationships between female and male in the woodland.
雄性繁殖能力受社群压力的影响，种群数量也随之受到影响。
The breeding capability of males and the population number of Rhombomys opimus are influenced by the social stress.
结果表明，随着草原兔尾鼠数量的下降，种群的年龄结构和繁殖结构都发生了明显的变化。
The result revealed that there was obviously changed in age structure and reproduction structure of L. lagurus with the decline of the population quantity.
深入地了解其独特的婚配行为机制、独特的繁殖发育机制，对有效地开展果蝠的保护工作、合理地控制种群数量有积极意义。
A detailed understanding to the particular mechanism of mating behavior, reproduction and development is effective to promote the protection of these fruit bats and to control their population.
因此，对野生扬子鳄种群繁殖机理和长期存在于高强度人为活动的压力之下的生存对策的研究，是恢复野生扬子鳄种群数量，使其免遭灭绝的关键。
The key to save the wild Chinese Alligator is to know the breeding mechanism of the remaining wild population and its survival strategy under such a serious human pressure.
初步分析表明大山雀对松毛虫种群密度变化有明显的功能反应，但由繁殖而引起的数量反应不明显。
Our data suggested that there are observable functional response of great tits to changes in moth densities but the numerical response caused by breeding are not obvious.
初步分析表明大山雀对松毛虫种群密度变化有明显的功能反应，但由繁殖而引起的数量反应不明显。
Our data suggested that there are observable functional response of great tits to changes in moth densities but the numerical response caused by breeding are not obvious.
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