Interplay of competition and facilitation in grazing succession by migrant Serengeti herbivores

Competition, facilitation, and predation offer alternative explanations for successional patterns of migratory herbivores. However, these interactions are difficult to measure, leaving uncertainty about the mechanisms underlying body-size-dependent grazing—and even whether succession occurs at all. We used data from an 8-year camera-trap survey, GPS-collared herbivores, and fecal DNA metabarcoding to analyze the timing, arrival order, and interactions among migratory grazers in Serengeti National Park. Temporal grazing succession is characterized by a “push-pull” dynamic: Competitive grazing nudges zebra ahead of co-migrating wildebeest, whereas grass consumption by these large-bodied migrants attracts trailing, small-bodied gazelle that benefit from facilitation. “Natural experiments” involving intense wildfires and rainfall respectively disrupted and strengthened these effects. Our results highlight a balance between facilitative and competitive forces in co-regulating large-scale ung..., , , # **Interplay of competition and facilitation in grazing succession by migrant Serengeti herbivores**

[https://doi.org/10.5061/dryad.7sqv9s4zk](https://doi.org/10.5061/dryad.7sqv9s4zk)

**Data S1. Serengeti_occupancy_data_4-day_2011-2018.** A compressed (zipped) folder containing eight .csv files, each labeled as ‘SER_20xx_final_dat_4d’ where 20xx is the year 2011 – 2018. Files contain the raw data aggregated within 4-day time intervals and are required to run a Bayesian occupancy model with the accompanying R script from the same year. Descriptions of columns names are as follows:

“NDVI.BIN” – a date (mm/dd/yyyy) which specifies the start of a 4-d period over the occupancy of migratory species is quantified; dates were selected to align with 8-d Normalized Difference Vegetation Index (NDVI) values provided by NASA’s MODIS satellite data. 

“X” – a unique numerical identifier

“NDVI.BIN.SITE” – the same date as in the NDVI.BIN column combined with the site ID.

“SITE” – the site ID of...