Greg Hofmeyr - Academia.edu (original) (raw)
Papers by Greg Hofmeyr
Proceedings of the Royal Society B: Biological Sciences, 2021
The deep sea has been described as the last major ecological frontier, as much of its biodiversit... more The deep sea has been described as the last major ecological frontier, as much of its biodiversity is yet to be discovered and described. Beaked whales (ziphiids) are among the most visible inhabitants of the deep sea, due to their large size and worldwide distribution, and their taxonomic diversity and much about their natural history remain poorly understood. We combine genomic and morphometric analyses to reveal a new Southern Hemisphere ziphiid species, Ramari's beaked whale,Mesoplodon eueu, whose name is linked to the Indigenous peoples of the lands from which the species holotype and paratypes were recovered. Mitogenome and ddRAD-derived phylogenies demonstrate reciprocally monophyletic divergence betweenM. eueuand True's beaked whale (M. mirus) from the North Atlantic, with which it was previously subsumed. Morphometric analyses of skulls also distinguish the two species. A time-calibrated mitogenome phylogeny and analysis of two nuclear genomes indicate divergence be...
Marine Mammal Science, 2018
Taxonomy plays an important role in conservation biology. Despite the variety of methods used to ... more Taxonomy plays an important role in conservation biology. Despite the variety of methods used to differentiate units, some groups, such as Delphinidae within the Cetacea have proven difficult to untangle. This study aimed to shed light on morphological variation of the genus Tursiops in South African waters using geometric morphometrics and to distinguish morphological groups and variation in these groups. A total of 241 crania of Tursiops spp. were analyzed using a suite of 2‐dimensional landmarks defined on photographs of the specimens. Results revealed two distinct morphological groups, with the smaller cluster comprised mainly of specimens from the cold temperate region off the west coast and the larger cluster comprised of specimens mainly from the warm temperate and subtropical regions off the south and east coast, respectively. We suggest that these groups correspond to different species of Tursiops, but this result requires further support. These groups were treated as separ...
Journal of Mammalogy, 2017
Marine Mammal Science, 2016
South African Journal of Wildlife Research, 2007
African Journal of Marine Science, 2012
African Journal of Marine Science, 2009
South African Journal of Science
Figure 1: Schematic of the ocean circulation south of Africa. Colours indicate surface (0-1000 m,... more Figure 1: Schematic of the ocean circulation south of Africa. Colours indicate surface (0-1000 m, red), intermediate (1000-1500 m, light blue) and deep (1500-4000 m, dark blue) pathways and their interconnectivity. In the South Atlantic, two northward flowing routes exist: the cold-water route which is the direct inflow from the Drake Passage, and the warm-water route southwest of South Africa. The three black lines highlight the main transects occupied by the SA Agulhas II during its annual relief voyages to the Prince Edward and Gough Islands and SANAE on the Antarctic continent. Measurement of the ionospheric dynamics by means of the ionospheric scintillation monitor on the SA Agulhas II provides a unique data set for studying the impact of the South Atlantic Magnetic Anomaly on ionospheric dynamics.
PLOS ONE, 2016
Many species of seabirds, including the only penguin species breeding on the African continent, a... more Many species of seabirds, including the only penguin species breeding on the African continent, are threatened with extinction. The world population of the endangered African penguin Spheniscus demersus has decreased from more than 1.5 million individuals in the early 1900s to c.a. 23 000 pairs in 2013. Determining the trophic interactions of species, especially those of conservation concern, is important when declining numbers are thought to be driven by food limitation. By and large, African penguin dietary studies have relied on the identification of prey remains from stomach contents. Despite all the advantages of this method, it has well known biases. We therefore assessed the African penguin's diet, using stable isotopes, at two colonies in Algoa Bay (south-east coast of South Africa). These represent over 50% of the world population. Various samples (blood, feathers, egg membranes) were collected for carbon and nitrogen stable isotope analyses. Results indicate that the trophic ecology of African penguins is influenced by colony, season and age class, but not adult sex. Isotopic niches identified by standard Bayesian ellipse areas and convex hulls, highlighted differences among groups and variability among individual penguins. Using Bayesian mixing models it was for the first time shown that adults target chokka squid Loligo reynaudii for self-provisioning during particular stages of their annual cycle, while concurrently feeding their chicks primarily with small pelagic fish. This has important ramifications and means that not only pelagic fish, but also squid stocks, need to be carefully managed in order to allow population recovery of African penguin.
Polar Biol, 2008
We observed a light coloured female southern elephant seal juvenile (Mirounga leonina) twice at M... more We observed a light coloured female southern elephant seal juvenile (Mirounga leonina) twice at Marion Island in August 2008 and conWrmed that it was leucistic rather than albinistic. Though there have been a few previous reports of light-coloured southern elephant seals, this is the Wrst conWrmed case of leucism in this species. Judged to be 1-year old, perhaps 2-years old at the most, and because we have not observed any leucistic pups at Marion Island during the past 2 years despite an extensive monitoring and tagging program, we think that this animal was born at nearby Prince Edward Island or perhaps further aWeld at Îles Crozet.
... Migrant and immigrant seals may also fall prey to the killer whale (Orcinus orca (L.)) popula... more ... Migrant and immigrant seals may also fall prey to the killer whale (Orcinus orca (L.)) population at MI which take elephant seals (Condy et al. ... 2009). Acknowledgements We thank field personnel of the Marion Island, Iles Crozet and Iles Kerguelen southern elephant seal ...
Proceedings of the Royal Society B: Biological Sciences, 2021
The deep sea has been described as the last major ecological frontier, as much of its biodiversit... more The deep sea has been described as the last major ecological frontier, as much of its biodiversity is yet to be discovered and described. Beaked whales (ziphiids) are among the most visible inhabitants of the deep sea, due to their large size and worldwide distribution, and their taxonomic diversity and much about their natural history remain poorly understood. We combine genomic and morphometric analyses to reveal a new Southern Hemisphere ziphiid species, Ramari's beaked whale,Mesoplodon eueu, whose name is linked to the Indigenous peoples of the lands from which the species holotype and paratypes were recovered. Mitogenome and ddRAD-derived phylogenies demonstrate reciprocally monophyletic divergence betweenM. eueuand True's beaked whale (M. mirus) from the North Atlantic, with which it was previously subsumed. Morphometric analyses of skulls also distinguish the two species. A time-calibrated mitogenome phylogeny and analysis of two nuclear genomes indicate divergence be...
Marine Mammal Science, 2018
Taxonomy plays an important role in conservation biology. Despite the variety of methods used to ... more Taxonomy plays an important role in conservation biology. Despite the variety of methods used to differentiate units, some groups, such as Delphinidae within the Cetacea have proven difficult to untangle. This study aimed to shed light on morphological variation of the genus Tursiops in South African waters using geometric morphometrics and to distinguish morphological groups and variation in these groups. A total of 241 crania of Tursiops spp. were analyzed using a suite of 2‐dimensional landmarks defined on photographs of the specimens. Results revealed two distinct morphological groups, with the smaller cluster comprised mainly of specimens from the cold temperate region off the west coast and the larger cluster comprised of specimens mainly from the warm temperate and subtropical regions off the south and east coast, respectively. We suggest that these groups correspond to different species of Tursiops, but this result requires further support. These groups were treated as separ...
Journal of Mammalogy, 2017
Marine Mammal Science, 2016
South African Journal of Wildlife Research, 2007
African Journal of Marine Science, 2012
African Journal of Marine Science, 2009
South African Journal of Science
Figure 1: Schematic of the ocean circulation south of Africa. Colours indicate surface (0-1000 m,... more Figure 1: Schematic of the ocean circulation south of Africa. Colours indicate surface (0-1000 m, red), intermediate (1000-1500 m, light blue) and deep (1500-4000 m, dark blue) pathways and their interconnectivity. In the South Atlantic, two northward flowing routes exist: the cold-water route which is the direct inflow from the Drake Passage, and the warm-water route southwest of South Africa. The three black lines highlight the main transects occupied by the SA Agulhas II during its annual relief voyages to the Prince Edward and Gough Islands and SANAE on the Antarctic continent. Measurement of the ionospheric dynamics by means of the ionospheric scintillation monitor on the SA Agulhas II provides a unique data set for studying the impact of the South Atlantic Magnetic Anomaly on ionospheric dynamics.
PLOS ONE, 2016
Many species of seabirds, including the only penguin species breeding on the African continent, a... more Many species of seabirds, including the only penguin species breeding on the African continent, are threatened with extinction. The world population of the endangered African penguin Spheniscus demersus has decreased from more than 1.5 million individuals in the early 1900s to c.a. 23 000 pairs in 2013. Determining the trophic interactions of species, especially those of conservation concern, is important when declining numbers are thought to be driven by food limitation. By and large, African penguin dietary studies have relied on the identification of prey remains from stomach contents. Despite all the advantages of this method, it has well known biases. We therefore assessed the African penguin's diet, using stable isotopes, at two colonies in Algoa Bay (south-east coast of South Africa). These represent over 50% of the world population. Various samples (blood, feathers, egg membranes) were collected for carbon and nitrogen stable isotope analyses. Results indicate that the trophic ecology of African penguins is influenced by colony, season and age class, but not adult sex. Isotopic niches identified by standard Bayesian ellipse areas and convex hulls, highlighted differences among groups and variability among individual penguins. Using Bayesian mixing models it was for the first time shown that adults target chokka squid Loligo reynaudii for self-provisioning during particular stages of their annual cycle, while concurrently feeding their chicks primarily with small pelagic fish. This has important ramifications and means that not only pelagic fish, but also squid stocks, need to be carefully managed in order to allow population recovery of African penguin.
Polar Biol, 2008
We observed a light coloured female southern elephant seal juvenile (Mirounga leonina) twice at M... more We observed a light coloured female southern elephant seal juvenile (Mirounga leonina) twice at Marion Island in August 2008 and conWrmed that it was leucistic rather than albinistic. Though there have been a few previous reports of light-coloured southern elephant seals, this is the Wrst conWrmed case of leucism in this species. Judged to be 1-year old, perhaps 2-years old at the most, and because we have not observed any leucistic pups at Marion Island during the past 2 years despite an extensive monitoring and tagging program, we think that this animal was born at nearby Prince Edward Island or perhaps further aWeld at Îles Crozet.
... Migrant and immigrant seals may also fall prey to the killer whale (Orcinus orca (L.)) popula... more ... Migrant and immigrant seals may also fall prey to the killer whale (Orcinus orca (L.)) population at MI which take elephant seals (Condy et al. ... 2009). Acknowledgements We thank field personnel of the Marion Island, Iles Crozet and Iles Kerguelen southern elephant seal ...