Kraai Unathi Masiobi, Tsvuura Zivanai, Tjelele Tlou Julius, Mkhize Ntuthuko Raphael, Kraai Manqhai
Centre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa. E-mail:
Agricultural Research Council, Animal Production, Range and Forage Sciences, Private Bag X 02, Irene, 0062, South Africa.
Zool Stud. 2022 Aug 12;61:e40. doi: 10.6620/ZS.2022.61-40. eCollection 2022.
Herbivory plays a fundamental role in determining the structure of savannas. The impacts of small and medium-sized mammalian herbivores on trees in savannas remain poorly understood because most research attention focuses on large herbivores such as elephants whose destructive effects on trees can be pervasive at landscape scales. On the other hand, feeding activities of generalist herbivores such as Cape porcupines on woody plants can lead to tree mortality. This study investigated the utilisation of woody plants by the Cape porcupine in three mesic savanna sites in South Africa. We determined the woody plant diet of the porcupine for the early and late dry seasons at Roodeplaat Farm in Gauteng Province, and at Goss Game Farm and Bisley Valley Nature Reserve in KwaZulu-Natal Province. Thirty and twenty randomly located quadrats (30 m × 30 m) were laid at Roodeplaat and Goss, respectively, while 10 smaller quadrats (10 m × 10 m) were laid at Bisley. We measured stem diameter and the length and width of bark scars made by porcupines on stems of woody plants. We collected ten dung samples from each study site in the wet and dry seasons for quantification of woody material in porcupine diet. Porcupine foraging behaviour impacted different tree species at each site: at Roodeplaat, at Goss and at Bisley. Each of these trees was dominant at each site. More scarring and tree mortality were recorded at Bisley with almost 70% tree sapling mortality occurring on trees that porcupine fed on. The size of bark scars was greater at Goss ( < 0.01) than at Roodeplaat and Bisley, which were similar. The area of bark damage on trees differed significantly by stem diameter size class ( = 0.007) and was greater for small stems (size class < 7.1 cm) than the larger stems (size classes 7.1-14 cm and 14.1-21). For all the study sites, dung samples revealed that woody material contributed over 80% of the porcupine diet during the dry season, but was lower at 35% during the wet season for Roodeplaat, although it was consistently high for Bisley at 79%. Porcupine foraging activities substantially contributed to tree mortality at each site. We posit that porcupine induced mortality on dominant tree species at each site may contribute to structural heterogeneity in woody plant vegetation in mesic savannas.
食草作用在决定稀树草原的结构方面起着基础性作用。中小型哺乳动物食草动物对稀树草原树木的影响仍知之甚少，因为大多数研究关注的是大型食草动物，如大象，其对树木的破坏作用在景观尺度上可能很普遍。另一方面，像南非豪猪这样的杂食性食草动物对木本植物的取食活动可能导致树木死亡。本研究调查了南非三个湿润稀树草原地区豪猪对木本植物的利用情况。我们确定了豪猪在豪登省鲁德普拉特农场、夸祖鲁 - 纳塔尔省戈斯野生动物农场和比斯利山谷自然保护区旱季早期和晚期的木本植物食谱。在鲁德普拉特和戈斯分别随机设置了30个和20个样方（30米×30米），而在比斯利设置了10个较小的样方（10米×10米）。我们测量了木本植物茎干的直径以及豪猪在茎干上留下的树皮疤痕的长度和宽度。我们在湿润和干燥季节从每个研究地点收集了10份粪便样本，以量化豪猪食谱中的木本物质。豪猪的觅食行为在每个地点对不同树种产生了影响：在鲁德普拉特、在戈斯和在比斯利。这些树中的每一种在每个地点都是优势树种。在比斯利记录到更多的疤痕和树木死亡情况，豪猪取食的树木上幼树死亡率几乎达到70%。戈斯的树皮疤痕尺寸比鲁德普拉特和比斯利更大（P < 0.01），后两者相似。不同直径大小等级的树木上树皮损伤面积存在显著差异（P = 0.007），小茎干（直径等级 < 7.1厘米）上的树皮损伤面积比大茎干（直径等级7.1 - 14厘米和14.1 - 21厘米）更大。对于所有研究地点，粪便样本显示在旱季木本物质占豪猪食谱的比例超过80%，但在鲁德普拉特，湿润季节该比例较低，为35%，尽管比斯利一直保持在79%的高水平。豪猪的觅食活动在每个地点对树木死亡有很大影响。我们认为豪猪在每个地点对优势树种造成的死亡率可能有助于湿润稀树草原木本植物植被的结构异质性。
