The first in the behind-the-scenes series for the Journal of Animal Ecology’s Animal Social Network Special Issue, this blog post is provided by Julie Turner (@WanderingBiol) and tells the #StoryBehindThePaper for the article “Early‐life relationships matter: Social position during early life predicts fitness among female spotted hyenas“, which was recently published in the Journal of Animal Ecology Animal Social Networks Special Issue.

Do you ever wonder about the inner workings of animals’ lives? Do they have lots of friends or are they loners? What is it like growing up as an animal? Do their behaviors have long-term consequences? These are some of the questions that we are lucky enough to get to address and observe with the Mara Hyena Project.

As hyena researchers, we always like catching up on the hyena “gossip” when we get together. Who is hanging out with who, who is getting picked on, who is a new mom, etc. The most interesting gossip to me is always around the relationships in the clan, and what does that mean for the individuals in it. Sponge’s mom doesn’t seem to care about him, so he doesn’t have many friends even though he is high ranking. Gaddafi is a particularly popular cub despite the fact she’s low ranking; she is one of the older ones in her cohort, so the younger ones don’t understand her rank yet [1,2]. I find this stuff fascinating. This interest in complex social behavior is what inspired the research. In our recently published paper, “Early‐life relationships matter: Social position during early life predicts fitness among female spotted hyenas,” we attempt to answer how social development of female spotted hyenas relates to their reproductive success and longevity [3]. We look at the social network positions of female hyenas as they grow up to see how their different types of relationships may influence how many children they have or how long they live.

Doing these analyses required us to do lots of field work to get the data. Driving around the Masai Mara every morning and evening, we stop every time we see a hyena. When they are in a group, we note who is there and record most of their behaviors that we see. Some of the most fun times doing this field work is when we sit at the den, which is the social hub of hyena society. There are frequently lots of cubs romping around, playing with other cubs and older siblings, chasing bugs, and nursing from their moms. It is lovely to watch everyone to the sound of insects as the sun rises and sets.

Importantly to answering questions about longevity and reproductive success, we were able to take advantage of the fact that the Mara Hyena Project has been collecting data this way for 30+ years. This means that thanks to many research assistants and graduate students, we have data on several generations of hyenas growing up, having offspring, and dying. We dug through this data to build social networks at three stages of hyena development – at the den (CD), juveniles not dependent on the den (DI), and early adulthood (adult) – to try to answer how the juvenile relationships of hyenas may influence their fitness.

We found that different types of relationships throughout development had important influences on development. The number of individuals that a female was around had a greater impact on her reproductive success but friendships had a bigger influence on the female’s longevity. Furthermore, the relationships females had as an adult had a stronger influence on their reproductive success than their juvenile periods, but the reverse is the case for longevity.

Monopoly was one of the females we followed through this analysis, so let’s take a look at her life. She was the granddaughter of the matriarch when she was born, so she was in the upper half of the hierarchy. Hyenas are very hierarchical, and it structures their lives [4]. She hung out with everyone in her cohort of cubs and those that visited the den. As a cub (CD), Monopoly was confined to the den and did not have much choice in who she could hang out with. However, she was particularly friendly with a subadult named Argon. Argon was a low-ranking subadult, and neither she nor Monopoly likely had a firm understanding of their rank in hyena society yet [1].

Once Monopoly became independent of the den (DI), she had more choice in who she could associate with as she could roam freely throughout the territory. Now she spent more time with her older sisters and cousins in particular. She was also friendliest with her cousins and two hyenas from another family, Gucci and her daughter Gelato.

As a young adult, Monopoly associated with many more individuals throughout the clan. She was a young, high-ranking lady and very popular. However, she still had her smaller group of friends that she had direct affiliations with. These friends ranged the rank spectrum, many were her relatives, but some were from lower ranking families. As an adult, Monopoly had one cub, Bonnet, and she lived to be a little over 4.5 years old when she was killed by eating from a poisoned carcass.

Through our research, we can see that hyenas have complex social interactions throughout their lives which have important repercussions for their fitness. Few other studies have looked at the role of juvenile relationships outside of primates, but these social positions clearly have important repercussions. We are still working to understand these fitness consequences and what mediates them.

References

1. Holekamp KE, Smale L. 1993 Ontogeny of dominance in free-living spotted hyaenas: juvenile rank relations with other immature individuals. Anim Behav 46, 451–466.
2. Smale L, Frank LG, Holekamp KE. 1993 Ontogeny of dominance in free-living spotted hyaenas: juvenile rank relations with adult females and immigrant males. Anim Behav 46, 467–477.
3. Turner JW, Robitaille AL, Bills PS, Holekamp KE. 2020 Early‐life relationships matter: Social position during early life predicts fitness among female spotted hyenas. J Anim Ecology 1695, 1–14. (doi:10.1111/1365-2656.13282)
4. Strauss ED, Holekamp KE. 2019 Inferring longitudinal hierarchies: Framework and methods for studying the dynamics of dominance. J Anim Ecology 61, 489–16. (doi:10.1111/1365-2656.12951)

Read the paper

Read the full paper: Turner, JW, Robitaille, AL, Bills, PS, Holekamp, KE. Early-life relationships matter: Social position during early life predicts fitness among female spotted hyenas. J Anim Ecol. 2021; 90: 183– 196. https://doi.org/10.1111/1365-2656.13282