[Reading level: C1 – Advanced]
Researchers disentangle complex connections among vegetation, herbivores, and dung in the South African savanna.
Animals eat plants. Animals poop. Poop nourishes plants. It may sound simple, but it’s not. Elizabeth le Roux, an ecologist and Newton International Fellow at the University of Oxford, studies this complex cycle in the South African savanna, particularly as it relates to larger animals and how they differ from small species in their effects on ecosystems.
As a graduate student at Nelson Mandela University in South Africa, le Roux began investigating how animal dung varies across the grassy plains of Hluhluwe-iMfolozi Park and whether that variation influences the local plant life. At 15 sites, she and her colleagues assessed the density of the vegetation, used camera traps to record how many of each animal species frequented a particular area and how long they stayed, surveyed the amount of dung and noted what species it came from, and sampled dung, soil, and plants to assess nitrogen and phosphorus levels.
BIG DUNG: Areas with denser vegetation and thus lower visibility (left) are more likely to be frequented by larger animals—which have less to fear from predators—than by smaller animals, according to a recent study. Compared with smaller herbivores such as impala, large herbivores such as elephants and rhinos produce dung with relatively lower phosphorus content. These differences in dung are associated with variable availability of nutrients for plants growing in the savanna, the researchers found, suggesting that the animals’ body sizes could influence ecosystem functioning.
The team hypothesized that vegetation-dense, low-visibility areas would be frequented by large animals, which are less likely to be targets for lions and other predators that sneak up in the foliage. Indeed, camera traps showed that smaller grazers such as impala stick mainly to open areas, while elephants and rhinos often graze at denser sites.
When it came to the animals’ dung, the team predicted that larger animals would excrete proportionally less phosphorus. That’s because larger animals have relatively larger skeletons, le Roux says, and thus may require more phosphorus from their food. This hypothesis, too, was supported by the data—phosphorus was scarcer in larger animals’ dung, both as a proportion of dung mass and relative to nitrogen content.
The researchers also analyzed the grasses at their sites to see if dung nutrient differences were reflected in plant tissue. Here, the data hinted that phosphorus:nitrogen ratios may be lower in grasses in vegetation-dense areas frequented by large herbivores, but the effect was weak. That’s not surprising, le Roux says, as plant nutrient ratios are influenced by factors other than dung, such as soil microbes and fire.
Ecologist Harry Olde Venterink of Vrije Universiteit Brussel praises the study for its innovative use of camera traps to collect quantitative data on animal behavior, and says it provides good evidence that larger animals are using sites differently than smaller ones and may be influencing nutrient availability via their dung. His team recently showed that herbivore dung quality in Europe influences plant community diversity (Sci Rep, 9:5675, 2019), and he says the new study is a further step toward deciphering how animals influence nutrient cycles.
However, Venterink questions some of the study’s assertions—in particular, the idea that species with larger skeletons need more phosphorus, a connection le Roux agrees isn’t well established. Venterink suggests that differences in dung nutrients could simply reflect differences in animals’ diets.
Le Roux says the findings could help researchers understand the effects of adding or removing larger species from ecosystems. As humans influence wild animal populations, often “we’re changing the average [body] size of the herbivore community,” she says. “We need to understand: What are the consequences?”
Source: https://www.the-scientist.com/the-literature/Herbivore-Body-Size-Influences-Grazing-Behavior-Poop-Quality-68082
WORD BANK
vegetation /ˌvedʒ.ɪˈteɪ.ʃən/ [C1] (n): thực vật
disentangle /ˌdɪs.ɪnˈtæŋ.ɡəl/ (v): gỡ rối
herbivore /ˈhɜː.bɪ.vɔːr/ (n): động vật ăn cỏ
dung /dʌŋ/ (n): phân
savanna /səˈvæn.ə/ (n): đồng cỏ xavan
poop /puːp/ (v, n): thải phân, phân
nourish /ˈnʌr.ɪʃ/ (v): nuôi dưỡng
ecologist /iˈkɒl.ə.dʒɪst/ (n): nhà sinh thái học
relate to sb/sth /rɪˈleɪt/ [C2] (v): liên quan đến ai/cái gì
ecosystem /ˈiː.kəʊˌsɪs.təm/ (n): hệ sinh thái
differ from sb/sth /ˈdɪf.ər/ [B2] (v): khác với ai/cái gì
effect /ɪˈfekt/ (n): ảnh hưởng
investigate /ɪnˈves.tɪ.ɡeɪt/ [B2] (v): điều tra
vary /ˈveə.ri/ (v): phân bố đa dạng
assess /əˈses/ (v): đánh giá
density /ˈden.sɪ.ti/ [C2] (n): mật độ
frequent /frɪˈkwent/ (v): thường xuyên lui tới
nitrogen /ˈnaɪ.trə.dʒən/ (n): nitơ
phosphorus /ˈfɒs.fər.əs/ (n): phốt pho
dense /dens/ [B2] (adj): dày đặc
visibility /ˌvɪz.əˈbɪl.ə.ti/ (n): tầm nhìn
be likely to do sth /ˈlaɪ.kli/ [B1] (adj): có khả năng là sẽ làm gì
impala /ɪmˈpɑː.lə/ (n): linh dương impala
content /ˈkɒn.tent/ [C2] (n): hàm lượng
associate /əˈsəʊ.si.eɪt/ [C1] (v): liên quan đến
nutrient /ˈnjuː.tri.ənt/ (n): chất dinh dưỡng
hypothesize /haɪˈpɒθ.ə.saɪz/ (v): đưa ra giả thuyết
target /ˈtɑː.ɡɪt/ (n): mục tiêu
sneak up /snik/ (phrasal verb): lẻn, lén lút
foliage /ˈfəʊ.li.ɪdʒ/ (n): tán cây, tán lá
stick to sth /stɪk/ (v): bám vào
graze /ɡreɪz/ (v): ăn cỏ
excrete /ɪkˈskriːt/ (v): bài tiết
proportionally /prəˈpɔː.ʃən.əl.i/ (adv): tương xứng
skeleton /ˈskel.ə.tən/ [B2] (n): khung xương, bộ xương
scarce /skeəs/ [C1] (adj): khan hiếm
analyze /ˈæn.əl.aɪz/ (v): phân tích
reflect /rɪˈflekt/ (v): phản ánh
tissue /ˈtɪʃ.uː/ (n): mô
hint /hɪnt/ (v): gợi ý
ratio /ˈreɪ.ʃi.əʊ/ [C1] (n): tỉ lệ
other than [C1]: ngoại trừ, ngoài, khác
microbe /ˈmaɪ.krəʊb/ (n): vi khuẩn
praise sb/th for sth/doing sth /preɪz/ [B2] (v): khen ngợi ai/cái gì vì điều gì
innovative /ˈɪn.ə.və.tɪv/ [C1] (adj): đổi mới, sáng tạo, cải tiến
quantitative /ˈkwɒn.tɪ.tə.tɪv/ (adj): định lượng
decipher /dɪˈsaɪ.fər/ (v): giải mã
assertion /əˈsɜː.ʃən/ (n): khẳng định
well established /ˌwel ɪˈstæb.lɪʃt/ (adj): vững vàng
ỦNG HỘ READ TO LEAD!
Chào bạn! Có thể bạn chưa biết, Read to Lead là một trang giáo dục phi lợi nhuận với mục đích góp phần phát triển cộng đồng người học tiếng Anh tại Việt Nam. Chúng tôi không yêu cầu người đọc phải trả bất kỳ chi phí nào để sử dụng các sản phẩm của mình để mọi người đều có cơ hội học tập tốt hơn. Tuy nhiên, nếu bạn có thể, chúng tôi mong nhận được sự hỗ trợ tài chính từ bạn để duy trì hoạt động của trang và phát triển các sản phẩm mới.
Bạn có thể ủng hộ chúng tôi qua 1 trong 2 cách dưới đây.
– Cách 1: Chuyển tiền qua tài khoản Momo.
Số điện thoại 0947.886.865 (Chủ tài khoản: Nguyễn Tiến Trung)
Nội dung chuyển tiền: Ủng hộ Read to Lead
hoặc
– Cách 2: Chuyển tiền qua tài khoản ngân hàng.
Ngân hàng VIB chi nhánh Hải Phòng
Số tài khoản: 012704060048394 (Chủ tài khoản: Nguyễn Tiến Trung)
Nội dung chuyển tiền: Ủng hộ Read to Lead
