Jonathan and Sasha graduate

Graduation time is a celebration of years of hard work. Today, it was the turn of Sasha Dines PhD and Jonathan Bell MSc. 

Sasha did her PhD on the use of acoustics to monitor populations of the Indian Ocean humpback dolphin (Sousa plumbea) - allegedly South Africa's most endangered mammal (other mammals may also be threatened). Her PhD worked involved years of deploying microphones into the sea in areas where the dolphins occur, and then trawling through thousands of hours of recordings listening for the occassional whistle or moan. Sasha found that acoustic monitoring might be a superior way of assessing the populations of Indian Ocean humpback dolphin as each individual has it's own signature whistle that can be recognised. 

Jonathan (aka JJ) spent several years looking into the perceptions of members of the public into how they perceived the right for access onto their properties to remove invasive species. Jonathan also looked into the best times in which to remove invasive Guttural Toads from urban properties. It turns out that the toads are most easily captured at night when the lights are on (not as simplistic as you might think!). 

We are very proud of the achievements of both Sasha and Jonathan and congratulate them again on their graduation. It has been  a privalege to have them as members of the MeaseyLab at Stellenbosch University. We look forward to hearing more about their achievements in future.

Dines, S. (2025) Applied passive acoustic monitoring of South Africa's most threatened marine mammal, the Indian Ocean humpback dolphin (Sousa plumbea). Stellenbosch University, PhD thesis

Bell, J.J. (2025) Right time, right place: a mixed method approach for invasive species management. Stellenbosch University, MSc thesis

Right time, Right place - in defense of his MSc thesis

Jonathan Bell used to work at NCC with his principle project being co-ordination of the Guttural Toad removal plan. During that time we had a lot of interactions and it was clear that Jonathan had great ideas of how to improve the efficiency of the eradication campaign. However, there was not a lot of time in his life for doing an MSc. Some years later though, Jonathan re-located to working for the Invasive Species Unit at the City of Cape Town, and there was a positive encouragement for him to do an MSc.

The idea for the first chapter of his project was to find out exactly why some people allowed access to their properties, and others did not. Using Jonathan's long list of contacts in areas invaded by the Guttural Toad and Polyphagous Shot-Hole Borer, he interviewed a series of different key informants to find out why they had or had not allowed access to their properties. The reasons were varied, but were aspects of socio-political, economic and environmental variables. Armed with their responses, Jonathan designed a questionnaire that he rolled out to 400 respondents in the City of Cape Town area. He found out that the type of Agents, Appointment Scheduling and Societal Influence were the most important categories chosen by people influencing whether or not they would allow access to their properties. Not only this, but he also found that these responses varied across an urban density gradient.

For his second chapter, Jonathan used a time to detection model (with the help of Dom Henry) to determine under what variables it would be most efficient to manage invasive Guttural Toads. This chapter too was a great success with several significant variables increasing the efficacy of contractors who were out to collect toads. 

Jonathan received a great mark for his defense presentation, and together with his thesis marks will graduate in March!

Congratualtions Jonathan!

School for Climate Studies (SCS) and Centre for Invasion Biology (CIB) Annual Research Meeting

Regular readers of this blog will be familiar with the CIB-ARM which is hosted annually in November. This year (after a 2 year interim), we see the new SCS-CIB ARM: a joint venture where Masters and PhD students present on their latest research. This event provides an important forum for networking for post-docs and students alike. For the CIB, the entire Core Team is invited to come together with their students from universities up and down South Africa.

Policy from Science

This year, there was a promient flavour of policy from science both at the national and international level. Prof. Melodie McGeogh (Monash University) provided a plenary from her perspectives after participating in the recent IPBES report Thematic Assessment Report on Invasive Alien Species and their Control. 

In addition, Peter Lukey (Chief Director: Environment Knowledge and Information at DFFE) provided an overview of his experience as a policy maker in the South African government.

In addition to these plenary talks, we had a host of marvellous talks from postgraduate students from the SCS and CIB. This included Jonathan Bell who presented an update on his MSc work on improving the efficacy of the Gutteral Toad eradication programme.

Another great ARM from another year of research for 10s of students working on invasions and climate change. We look forward to next year when the intersection of these two disciplines will be dissected in more detail.

A testimonial from Sam and the importance of saying thank you

Today was another long day. I got back from the office to find a whole bunch of messages on different platforms and I made myself a cup of tea before sitting down and going through them. One was a voice note from Sam Peta. Sam did a MSc with me and James Baxter-Gilbert, defending his thesis back in 2022 (see here). The voice note really surprised me. I've asked Sam, and he's given his consent to transcribe it here for the blog:

“Morning John, I hope you're good.

I think I forgot to tell you this but some time last year I had a job interview. I think it was a research field assistant for the Cape Parrot Project in Hogsback. It was like a brief interview to ask about who I am and what I do what was my MSc was about.

I told the lady, I don't remember her name, that I was supervised by Prof John Measey, and she said “Oh, I know John Measey!”

I was like whoa, okay, that's nice. And then she started telling me about her project with the leopard toad and that was quite amazing.

Even with one of the guys that I work with, he said that you taught him, I think when he was in Stellies.

So yeah, I think that the point that I'm trying to make is that I wouldn't be where I am now if it wasn't for you. The amazing skills that I've learned from you, the amazing mindset that I have when it comes to research, or looking at the world the way I look at things. So I'm grateful for the support that you've given me all these years, and now I have the confidence to say that I would like to believe that there's a great future in terms of research, and in terms of finding my way around. They're the small parts of life when it comes to working, is because of the skills that I've learned from people like you and James [Baxter-Gilbert] have helped me so much. I'll forever be grateful for that.

Even when I hear people talk about you, I get that kind of inspiration to say, okay, I've been under the supervision of one of the most incredible scientists in the world. So yeah, I'd like to believe that, hopefully in some way we can just keep in touch enough to work together at some point in the future. Yeah, I'm just wanting to say, before I start my new working day, thanks so much John for everything.”

Firstly, I’m incredibly grateful to Sam for reaching out and saying such nice things. It’s so great to hear that there’s been a lasting positive effect on students that have worked in my lab. Second, is that I have learned that it’s so very important to actually say these things to people. To actually thank them instead of just thinking that it would be nice. It’s not just important that they hear you say it, but also because you might be surprised what you hear in reply.

Here’s my response to Sam:

“Hey Sam – Thanks so much for your kind words. I think what you forget is that this does not only go in one direction. I learn an incredible amount from my students, including you. This is one of the things that makes being an advisor such an enjoyable experience, because I get to work with such enthusiastic people. It’s really my privilege to have worked with you.”

I used to think when I heard aged professors talking about their wonderful postgraduate students that they were just paying lip service to the team of people who really did all the work, but with no thanks. However, what I’ve learned, over the fullness of time, is that for many professors they truly do appreciate their team and the benefit goes both ways.

So, if you have read this far and you have someone in your life that you are thinking – yeah, they really helped me – I’m asking you to reach out to them now and say thank you. If you can, leave a voice note (like Sam did) so that they can hear your voice and know that you really do mean it. It will mean so much to them, and like Sam you may well get some words of wisdom to continue to propel you forwards.

The 10th World Congress of Herpetology in Kuching, Sarawak, Malaysia

It was a great pleasure to attend the 10th World Congress of Herpetology in Kuching this month. The congress was a great opportunity to catch up with herpetologists from across the planet, including many that I have known for many years as well as many many new faces. 

I presented my work on the gut microbiome of Xenopus laevis, and was pleased to see many former members of the MeaseyLab presenting their own work.

Burrowing in Snakes: a Comparative Study on the Performance and Mechanics of Snake Burrowing
Anthony Herrel, David J. Gower, James C. O’Reilly, Nathan J. Kley, Philippe Gaucher, Ilian Grima, John Measey and Marion Segall

Snakes are an incredibly diverse lineage of squamates that have radiated into a great diversity of habitats from a possibly fossorial ancestor. Fossoriality imposes strong constraints on obligatory head-first burrowers and this has been suggested to have impacted the morphological evolution of both head and cranial shape. The strength of constraints on head shape likely depend on the taxon and burrowing style but quantitative data on the forces exerted during burrowing or the kinematics of burrowing remain scarce. Preliminary data suggested that typhlopid snakes were capable of generating higher forces than other snakes for a given size and body diameter but taxon sampling was limited. Here, we present data on the three-dimensional burrowing forces for 26 species of snakes distributed across most major lineages. We further present the first X-ray data on the kinematics of locomotion through tunnels and soil for a subset of species including sand swimmers (Eryx) and true burrowers (Anilius, Xenopeltis, Cylindrophis, Homalopsis and Aspidelaps). Our data show significant differences in maximal resultant forces and force orientation in different species. Moreover, our kinematic data show that sand swimmers are unique in showing kinematics of subsurface locomotion similar to those observed in snakes swimming in water. Finally, we show that some snakes such as Anilius are capable of performing internal concertina locomotion documented previously only for caecilians. Overall our data shed new light on the diversity of burrowing performance and kinematics in snakes and help understand the evolution of this lifestyle and its constraints on form and function.

Does Plasticity or Genetic Adaptation Induce Variation in Thermal Sensitivity of an Invasive Frog (Xenopus laevis)? A Population Level Study, from Tadpoles to Adults
Laurie Araspin, John Measey and Anthony Herrel

Life history traits of organisms are modulated by the selective pressures of the environment, generating variation in phenotypes. This phenotypic diversity can be observed at the interspecific level but also at the intraspecific level in populations living in different environments. Temperature is a characteristic of an animal’s habitat and one of the dimensions of the ecological niche. It is a critical factor impacting all aspects of the biology of organisms, especially in ectotherms. Xenopus laevis is an aquatic frog that is invasive on four continents, with invasive populations inhabiting a diversity of environments. The objective of this study was to investigate the thermal adaptation ability of this species that is successfully established in dramatically different thermal environments. The use of thermal performance curves allowed to assess the relationship between temperature and locomotor performance and basal metabolic rate in individuals from two generations. Phenotypes from a F1 generation of the studied populations raised in a common garden environment were compared to the F0 phenotypes. This allowed to understand whether the observed differences among populations
are plastic or genetically based. This study demonstrated that populations exhibit a different thermal dependence of their performance, and that genetic and plastic processes are involved in the thermal adaptation, highlighted by a significant genotype by environment interaction. Variation in performance depending on temperature provides an insight into how this invasive species can survive and cope with different thermal environments, especially in the context of climate change.

Of Toads and Toxins: Shrinking Toxin Glands but Stable Toxin Composition Indicate Directions and Constraints of Adaptation in Invasive Populations of an African Toad
Max Mühlenhaupt, Cláudia Baider, James Baxter-Gilbert, André J. de Villiers, Nhlanhla S. Dludla, F. B. Vincent Florens, Buyisile G. Makhubo, Xavier Porcel, Julia L. Riley, Willem A. L. van Otterlo and John Measey

Many amphibian species use chemical defenses to avoid predation, yet, how these defenses vary between populations, or change as populations colonize novel habitats is not well understood. The Guttural Toad (Sclerophrys gutturalis) has established three invasive populations, located in Mauritius, Réunion, and Cape Town. All of these populations originated from a clade located at the port city of Durban in eastern South Africa, providing an excellent study system to examine how biological invasions drive phenotypic change. To investigate how toad chemical defenses may have shifted along their invasion path, we compared the relative size of the parotoid glands (as a correlate of toxin quantity) and the composition of the toxic secretions that exude from these glands (as an indicator of toxin potency) between native and invasive populations. While the two oldest invasive populations, Mauritius and Réunion, showed pronounced convergent decreases in gland size, the toxin composition remained stable between all populations. These results indicate that the invasive populations of this chemically defended toad may have experienced reduced predation pressure in their novel habitats, which resulted in reduced selection pressure for defense. Furthermore, within the native populations, gland size may also be a more variable trait than toxin composition. Integrating both quantitative as well as qualitative information will help us better understand the evolution of chemical defenses in animals and could aid in predicting if and how chemically defended invasive species colonize novel environments.

Home and Away: The Core Gut Microbiome of Xenopus laevis is Modified by its Environment
Measey, J., Ren, Q., Guille, M., Almojil, D., Araspin, L., Wagener, C., Boissinot, S., Watts, J. and Robson, S.

The vertebrate gut microbiome is a community largely composed of bacterial, fungal and viral components, whose molecular component equal that of the host. The influence of the microbiome is known to be significant both on an individual basis, and also on population scales in a wide range of host organisms. The gut microbiome is known to be involved with key attributes of animal health, including assimilation of nutrients, immuno-defensive functions and host behavior. In this study, we used bacterial 16S rRNA amplicon-based sequencing for metataxonomic classification of the gut microbiome of individuals from eight populations of Xenopus laevis. These populations were selected to represent an altitudinal gradient in the native range of the host species (0 to 3,000 m asl). From the 16S rRNA community profiles, we determine the components of the core microbiome of X. laevis , and ask whether deviations from the core are associated with the environmental context in which they live. In addition, we sampled four European invasive populations and a laboratory population from the European Xenopus Resource Centre (EXRC) in the UK, to determine what aspects of the core microbiome are retained by non-native populations. This represents the first time that the microbiome of X. laevis has been assessed across such diverse conditions, and provides data that will help understand the role played by the environment and inform monitoring of health within this model organism.

ROUNDTABLE "TAKING THE INVASIVE TOAD TOOLKIT GLOBAL"

John Measey, Georgia Ward-Fear & Angelica Crottini

Invasive toads are a global problem, and yet many solutions and mitigations are available –
particularly as a result of a large investment into cane toad invasions in Australia. But how
much of the “invasive toad toolkit” can be exported to other invasions? This round-table event
is aimed at stakeholders with an interest in toads and toad invasions to precise what parts of
the toad toolkit can be used in toad invasions worldwide.